Jan 31 2014

Repetitive Math Questions in GMAT Official Guides

GMAT Official GuidesIn your preparations for the GMAT math section, it is essential that you practice with retired real GMAT questions using the GMAT Official Guide (13th Edition) and the GMAT Quantitative Official Guide (2nd Edition). These two books provide you with a combined total of 430 Problem Solving and 322 Data Sufficiency practice questions.

Repetitive Problem Solving Questions

One interesting observation from our analysis of these questions is the frequency with which some questions closely mirror another question. Due to copyright issues, we cannot reprint these repetitive math questions from the Official Guides. But if you have your copies handy, compare the following sets of Problem Solving questions:

  • 13E #128 (page 170) vs. 2E #132 (page 79): These two questions involving combinatorics are nearly identical, even using the same numbers in the problem and in the first three answer choices (one of which is the correct answer). Only the context changes: one question involves finding the minimum number of colors for a distribution center’s coding, and the other involves finding the minimum number of letters for an experiment’s coding.
  • 13E #194 (page 179) vs. 2E #165 (page 84): Both questions provide three fractions of a total amount and the remaining balance that is unaccounted for, and ask us to calculate the total amount. One question relates to the amount of a trust fund whereas the other involves the number of students in a class, but the numbers within the problems are identical (except that one total is in thousands and the other is not).
  • 13E #124 (page 169) vs. 13E #133 (page 171) vs. 2E #56 (page 69): These three questions all involve calculating the number of pairs that are possible out of a larger group. Two of these questions ask about the number of table entries needed to show the mileage between any two cities, and the third asks about number of games needed so that every team in a league plays each other once. For these types of questions, we teach our students a tabular approach, a combinatorics approach, and a summation approach.
  • 13E #137 (page 171) vs. 13E #203 (page 181): At first glance, these two word problems seem unrelated. But the setup for both problems is identical: we have an unknown price and quantity, and when one goes up by a specified amount the other goes down by a specified amount in order to generate an equivalent revenue amount.
  • 13E #111 (page 167) vs. 13E #170 (page 176): In both cases, we have a terminating decimal in the form of 1 / (2^x * 5^y) where x and y are specified exponents. Both questions entail counting digits.
  • 13E #95 (page 165) vs. 13E diagnostic #13 (page 22): Both questions entail one positive integer divided by another, resulting in a quotient and a remainder equivalent to .12. Our objective is to use the .12 to deduce the value of the divisor in one question and to identify a possible remainder in the other question.
  • 13E #45 (page 158) vs. 2E #57 (page 69): Both problems give us a quadratic equation using the variable x and a constant k. Given one root of the quadratic, we must find the other solution in one problem and the value of k in the other problem.

Repetitive Data Sufficiency Questions

Although the above are the most obvious examples of repetition in Problem Solving, there is much more repetition of concepts across questions. We also can find examples of repetition within Data Sufficiency, albeit to a lesser extent. As two obvious examples, compare the following sets of Data Sufficiency questions:

  • 13E #2 (page 275) vs. 13E #21 (page 276): These two questions have identical setups, although with different numbers in different contexts. In both questions, statement 1 gives us what percent of women have a certain characteristic and statement 2 gives us what percent of men have the same characteristic. The questions both ask what percent of the total are women with that characteristic.
  • 13E #57 (page 280) vs. 13E #59 (page 280): In both cases, we have two different denominations (of bills in one question and of gift certificates in the other). Statement 1 has an identical setup in both questions – the maximum number of the smaller denomination. In #57, the initial information tells us the minimum number of the larger denomination and statement 2 tells us the total value of both denominations combined. In #59, the initial information and that given in statement 2 are swapped.

Conclusions

Why does this repetition happen? Since the GMAT tests a finite number of concepts, these concepts will inevitably appear repeatedly in various forms. But since the GMAC must produce a vast number of questions each year to ensure a fair testing environment, one way to make the question development process more efficient is to borrow heavily from other questions. We also see concepts applied repetitively in Verbal questions, but the questions themselves are not as obviously duplicative as the Math questions that we’ve discussed.

What is the implication of this? One of our “6 Habits of Highly Effective GMAT Students” is to watch out for patterns. As you work through many practice GMAT problems in the Official Guides and elsewhere, you will inevitably encounter similar concepts. With sufficient practice, you will be able to identify the approaches that are most relevant to a given problem. Of course you should not blindly follow the same methodology used on another problem, since the concepts may be applied differently. But the more adept you are at quickly recognizing the relevant approaches to apply to questions on test day, the better your GMAT score will be.

Oct 30 2013

Like Versus Such As

Like vs Such AsIdioms are one grammatical component of GMAT sentence correction problems. Furthermore, the GMAT tests meaning, part of which is appropriate word choice. One issue that the GMAT has previously tested is the usage of like versus such as. When giving an example, we should use such as: John collects pictures of sports cars made by companies such as Lamborghini and Maserati. When indicating similarity, we should use like: A giraffe’s neck is like that of a brachiosaurus.

Difference Between Like and Such As

Although like has come to be used synonymously with such as in common usage, there is an important distinction that is too often overlooked. In particular, like implies similarity but exclusion whereas such as implies inclusion. Using like is appropriate only if the action pertains to nouns similar to our referenced noun but specifically excludes the referenced noun. As an example: Movies today often feature heroic actors like John Wayne. This usage is correct because movies today feature actors similar to John Wayne, but do not feature John Wayne himself. On the other hand, we could say: Movies today often feature heroic actors such as Brad Pitt. In this sentence, such as is appropriate because Brad Pitt is both an example of a heroic actor and is included in the list of heroic actors today. Here is an interesting article from Grammar Girl that expands on this point.

Incorrect Usages of Like

In October alone, I have come across at least 100 incorrect usages of the word like in the context of providing an example. In every one of these instances, such as would be a better choice. To me, hearing the work like used in this manner is like hearing fingernails scratching a chalkboard. Here are just a few examples that I have come across, including a couple which appropriately use such as:

  • An October 8 article about Samsung in The Wall Street Journal: “Samsung has evaluated startups such as Unity Technologies … and Green Throttle Games.” Yet the next sentence of the same article states: “It has also considered gaming pioneer Atari Inc., which Samsung could have used to offer classic games like Asteroids and Ping Pong.”
  • A Google help page for its AdWords product: “Choose words or phrases relevant to your product or service so your ads appear when customers use those terms to search on Google or search partner sites, like AOL.”
  • An article in the October issue of Entrepreneur magazine about the OwnerListens app: “After 15 years of building companies such as Hotbar.com and SmartShopper.com, Oren Dobronsky checked out of technology and into hummus.”
  • The next article in the same issue of Entrepreneur magazine, written by the exact same author: “Ephraim signed on with London-based GoSquared, an analytics platform designed to demonstrate how people use a site, tracking key information like where individual visitors are from, what brought them to the site and how they view a page.”
  • An earthquake preparedness flyer from ReadyOC: “Your bucket list consists of basic items you’ll need in case of emergency – like an earthquake or wildfire.”
  • An article about cruising from the November/December issue of AAA magazine Westways: “On some luxury lines, items like bar drinks, tips, and even shore excursions are included.”
  • The featured article in the Personal Journal section of the October 30 issue of The Wall Street Journal: “Marc Forgione creates a tableside ‘cloud’ of truffle broth with dishes like squash ravioli and rabbit Bolognese at his New York restaurant.”
  • An article about study-abroad programs, also in the October 30 issue of The Wall Street Journal: “But students might be missing out on some important life experiences, like learning to be self-reliant and adaptable…”
  • The privacy policy of another GMAT preparation company: “Our site’s secure registration form requires users to give us contact information, like their name and email address.” “We do not store financial information like credit card numbers or personal information like social security numbers on this site.”

Correct Usages of Like

Does the word like ever get used correctly? Here are two usages that appropriately convey that one noun is similar to another. This is typically how we see the word like used correctly on GMAT Sentence Correction.

  • An article in the October 28 issue of Forbes about the 50 best small companies: “Like j2, Stamps.com rediscovered its greatest strength in a core business.”
  • An article in the October issue of Inc. magazine: “Innovative culture is like karaoke.”

Like a sunny day, all good things, such as this article, must come to an end. So I’ll leave you with this final thought: When taking a standardized test such as the GMAT, avoid using the word like to indicate an example.

Sep 27 2013

Fractions are Critical to GMAT Math

Fractions are critical to GMAT mathAn interesting article on fractions appeared this week in the Wall Street Journal. You must be thinking: fractions? interesting? Well, it’s interesting at least for those of us who teach the GMAT.

According to the article, “national tests show nearly half of eighth-graders aren’t able to put three fractions in order by size.” Can you? Here’s a Problem Solving question from the 2nd Edition of the GMAT Quantitative Official Guide.

Which of the following is greater than 2/3?
(A) 33/50
(B) 8/11
(C) 3/5
(D) 13/27
(E) 5/8

Methods to Compare Fractions

By definition, only one answer can be correct, and therefore only one answer can be greater than 2/3. So we are essentially looking for the biggest of these five fractions. There are two common methods by which to compare fractions: find a common denominator and then compare the numerators OR convert the fractions into decimals. Two more subtle approaches are comparing the fractions to a point of reference (such as 1/2) and finding a common numerator in order to compare the denominators.

Solution to Problem

For this problem, finding a common denominator seems messy. We can quickly eliminate (D) by noting that 13/27 < 13/26 = 1/2 < 2/3. For the remaining answers, it’s best to convert them into decimals. In order to save time, we don’t need to convert them all into decimals. We just need to find one that is greater than 0.6666 (the decimal equivalent of 2/3). So we should start with whichever answer seems the biggest.

GMAT Genius recommends that you memorize the fraction-to-decimal conversions for halves, thirds, fourths, fifths, sixths, eights, ninths, tenths, and elevenths. If you know these conversions, we can quickly identify (B) as the correct answer. 1/11 = 0.090909. To find any other eleventh, just multiply the numerator by 9. So 8/11 = 0.727272, which is clearly more than 2/3. For the record, (A) 33/55 = 0.66, (C) 3/6 = 0.6, and (E) 5/8 = 0.625. But again, once we have identified (B) as the correct answer, we should not spend our time with these additional conversions. Let’s save those precious few seconds for other problems.

Benefits of Fractions

Although this is admittedly an easy question by GMAT standards, fractions are essential to the GMAT math section. Fractions tend to make calculations easier than decimals, because numbers often conveniently cancel out when using fractions. Fraction calculations can appear directly and indirectly on all types of GMAT math problems, not just on basic arithmetic problems. As Dr. Bob Siegler of Carnegie Mellon University states in the Wall Street Journal article, “If you don’t understand fractions, it’s literally impossible for you to understand algebra, geometry …”. So be sure to study your fractions!

Jul 03 2013

My New GMAT Score: 770

GMAT Score 770I retook the GMAT in late May, because I had not yet taken the Next Gen GMAT with Integrated Reasoning. My new GMAT score is 770, same as my prior score. My scaled section scores are Q51 and V42. My AWA score remains a perfect 6 and my IR score is a perfect 8. Based on this testing experience, there are some observations that I can share. Obviously I cannot share information about specific questions that I saw in my examination. Please also keep in mind that because every GMAT administration is different, your experience may vary.

Pre-Test Experience

My test day didn’t start off well, as my son woke me up more than an hour earlier than usual. So I was a bit tired and cranky, despite having gone to sleep early the prior night. For breakfast, I ate two Sausage McMuffins with Egg from McDonald’s. Not the healthiest breakfast, but I recommend lots of protein for mental concentration. I then completed a few light errands, avoiding anything that would be mentally taxing. I then drove to the testing center, stopping at a different McDonald’s for a light lunch; I ate only the grilled chicken inside a McWrap. I also drank a Coke Zero, as I needed some caffeine after the early awakening.

My test time was 12:15 pm at the Pearson center in Lake Forest, CA. I liked the Lake Forest location more than Pearson center in Anaheim, where I have gone previously. The Lake Forest location seemed quieter, calmer, brighter, and more welcoming than I remember the Anaheim location to be. The Pearson staff was very friendly and helpful. I arrived at the center 30 minutes in advance of my appointment time, as recommended. I was promptly checked in, and since a workstation was available, I was seated for my test around noon. Although I felt a little nervous before the test, some deep breaths and positive affirmations helped me quickly overcome any stress and focus fully on the test.

During the GMAT

During the 8-minute breaks, it took about one minute each time for the test proctor to notice that my hand was raised and to come escort me out of the testing room. I had already scoped out the restroom and asked permission to use it during the breaks. My break routines followed exactly what is outlined on our Taking the GMAT page, with the entire routine taking about five minutes each time. For each snack, I had half a cheese stick and a few sips of Gatorade. I made sure to get checked in and escorted back to my workstation with at least one minute to spare each time.

On test day, Integrated Reasoning, the entire math section, and Reading Comprehension turned out easier than I expected. On the other hand, Sentence Correction and Critical Reasoning were harder than I expected. This is reflected in a lower verbal scaled score than I expected (especially compared to the V49 that I received using GMATPrep). My expectations were based primarily on my familiarity with GMATPrep and the Official Guide. Keep in mind that I was expecting very hard questions on the adaptive math and verbal sections, consistent with a 99 percentile score. Yet the difficulty of some SC and CR questions still surprised me. Let me elaborate a bit for each section.

Observations About Test Sections

AWA

The Analysis of an Argument essay was very straightforward, as expected. The most helpful form of AWA preparation is to write full essays for several prompts picked at random from the Official List of essay topics.

Integrated Reasoning

As described in my prior post about the 105 official GMAC practice IR questions, difficulty for the practice questions varies but includes some very challenging questions. The IR questions in some third-party (non-GMAC) diagnostics are even harder and far more calculation-intensive. In my practice, I had consistently found it challenging to complete 12 IR questions within the 30-minute time limit. By contrast, the 12 IR questions that I saw on the real GMAT were relatively straightforward. I would not rate a single of these questions as difficult. No question took more than 3 minutes to complete. Based on the GMAC practice questions, I was not expecting to use the calculator much. In fact, I only used the calculator for some basic calculations on two of the 12 questions.

Math

Question difficulty overall was easier than I expected, although still challenging. I had faced harder questions in GMATPrep and elsewhere. Due to careless errors and other mistakes, Q50 was the highest I had scored with practice diagnostics. Since several questions on the real test seemed quite straightforward and because the math section is adaptive, at times I wondered whether I messed up along the way. Fortunately this was not the case. The easier difficulty was seen in both Problem Solving and Data Sufficiency questions, and across all types of math concepts.

Verbal

Reading Comprehension was a bit easier than expected, mainly because three of the four passages were shorter than diagnostic test passages. Some RC questions were subtle but not extraordinarily difficult. Sentence Correction and Critical Reasoning, however, contained some very challenging questions. Fatigue may have set in by the time I reached the Verbal section, compounding the difficulty. A few tricky SC questions underlined only a few words, and I struggled to determine the best construction between two possible answers. On a few tricky CR questions, none of the answers seemed appropriate (a situation I have rarely faced) and I needed to make a best guess. I was hoping that these were experimental questions, but based on my final verbal score, that doesn’t seem to have been the case.

Final Notes

As a final note, the free preparation advice on the GMAT Genius website is completely solid – nothing changes based on my test experience. I followed the advice that we offer, and this advice served me very well. Similarly, the math and verbal concepts that we teach to our clients remain perfectly applicable. No additional concepts were required to answer the questions that I saw, nor does our material contain extraneous content. Every GMAT experience is different, but hopefully these insights will help in your preparations.

Jun 05 2013

105 Official Integrated Reasoning Questions

GMAT Integrated Reasoning AnalysisIn honor of Integrated Reasoning’s one year birthday on June 5, we decided to carefully evaluate all 105 official IR questions that the GMAC has made available for practice so far. This includes 50 questions in the Official Guide online companion, 12 questions in the GMATPrep diagnostic tests, 15 questions in the GMATPrep practice question sets, and 24 questions in the Question Pack 1 add-on to GMATPrep.

In addition, MBA.com offers 19 sample Integrated Reasoning questions, of which 15 are duplicative with Official Guide online questions and four are not found elsewhere. You can also find links to these questions on our Integrated Reasoning page. Note that the fourth question in the Graphics Interpretation problem set, the third question in the Two-Part Analysis problem set, the third question in the Table Analysis problem set, and the first question in the Multi-Source Reasoning problem set are the unique problems. These four questions combined with the 101 questions listed previously make up the 105 questions that we reviewed.

General Lessons Learned

So what lessons did we learn? Let’s first discuss some general thoughts, and then observations specific to each question type. Overall, Integrated Reasoning can be quite challenging even though this section is not adaptive. Difficulty varies from relatively straightforward to insanely difficult (given the time constraints). Insanely difficult questions would take even the most advanced students more than 3 minutes to correctly answer. Let’s hope that the GMAC balances question difficulty amongst test takers. Although difficulty varies within each question type, we would rank the four question-types from easiest to hardest as follows: Table Analysis, Graphics Interpretation, Two-Part Analysis, Multi-Source Reasoning.

Pacing

The time crunch is real, and you must be careful not to spend excessive time on any one question. Unless you are aiming for a perfect 8 score, you may be better off skipping (i.e. quickly guessing on) one very difficult question (if you can quickly make that assessment of difficulty) and saving your time for other questions. Since you must get all parts of a question correct, skip the entire question if you are short on time; don’t waste time trying to get non-existent partial credit. If you do need to skip a question, it’s better not to skip a Multi-Source Reasoning question. Since you typically see the same MSR prompt for multiple questions and because reading the MSR prompt takes most of the time, you won’t actually save much time by skipping an MSR question.

The Calculator

Although a calculator is available, its use can itself be time-consuming and is usually not necessary. On the practice questions, we rarely used the calculator, usually on just one part of one or two questions out of 12 questions. The calculator proved helpful only on a truly mathematically intense calculation that could not easily be estimated or compared with another value. We found ourselves using the calculator more on Graphics Interpretation than other question types, albeit still infrequently. Some third-party (non-GMAC) diagnostics contain IR questions that are far more calculation-intensive, and therefore more in need of the calculator, but this is not reflective of the real GMAT.

Read Carefully

The wording of problems is purposely subtle and tricky. Be sure to read the prompt, the question, and the answers very carefully. Unlike the math section of the GMAT, you will find lots of extraneous information and data on Integrated Reasoning, particularly for Multi-Source Reasoning and Table Analysis questions. Get a good overview of the information presented and then extract the relevant information.

Graphics Interpretation (GI) [23 of the 105 questions]

GI questions deal primarily with math concepts. Line slopes and percents are particularly prominent in this question type, with ratios, mean averages, and probability also appearing frequently. All types of graphs can be included with GI questions, from the more familiar bar charts and line graphs to less familiar types of graphs such as specialized flowcharts and bubble charts. In order to save time on GI, look at drop-down menu choices before doing any work. As with Problem Solving questions, you will often find multiple-choice answers that are far apart, in which case approximation is appropriate.

Two-Part Analysis (2P) [34 of the 105 questions]

Versus the other IR question types, 2P questions vary most significantly in the information presented and the question asked. 2P is about evenly split between math-focused and verbal-focused questions. Each verbal-focused question is generally similar to either a Reading Comprehension question or a Critical Reasoning question (all types, but strengthen and weaken types are most common). Although the format of the question is slightly different, the skills used to answer 2P verbal-focused questions are pretty much the same as the skills used in RC and CR. As described in our prior post, we found two 2P verbal-focused questions with questionable answers in the Official Guide online companion. Because the Official Guide was released before the Integrated Reasoning section launched, these two questions probably did not receive the same level of rigorous testing that GMAC questions usually get.

For the 2P math-focused questions, a wide variety of math concepts are present, including geometry, algebraic equations, rates, and functions. As with Problem Solving questions, we generally don’t find much irrelevant information, so be careful if you haven’t used all the numbers or data provided. The difficulty of the math-focused sample questions skews harder than that of the verbal-focused sample questions, but the sample size is not large enough to draw any definite conclusion. You should work through 2P practice questions to become familiar with the question format. But because 2P questions vary widely, the best way to prepare for the concepts tested in 2P questions is to prepare for the GMAT math and verbal sections.

Table Analysis (TA) [14 of the 105 questions]

TA questions are primarily about figuring out the best way to sort the table. Tables can be large and contain lots of extra data, but sorting helps you quickly extract the relevant data. When first approaching a TA question, understand what information the table contains at a big-picture level without delving into the numbers. For each of the three sub-questions, sort the table based on what you are asked. Trying to answer a question without sorting will just waste time.

TA questions deal primarily with math concepts, particularly with mean and median averages and with ranges. Questions are almost always yes/no or true/false, so you typically don’t need to calculate exact values. You often must make some sort of comparison (e.g. is the mean value for 2010 greater than the mean value for 2011?), but this can usually be done without precise calculations.

Multi-Source Reasoning (MSR) [34 of the 105 questions]

MSR is particularly hard, because the information and data is spread across two or three tabs, only one of which is viewable at a given time. In order to alleviate the need to switch back-and-forth, take notes on your whiteboard packet of the important points on the least important or least data-filled tabs. You typically see the same MSR prompt for multiple IR questions (as with Reading Comprehension), so carefully read the MSR prompt the first time you see it, even if doing so consumes extra time.

About 2/3 of the sample MSR questions are verbal-focused and about 1/3 are math-focused. The verbal-focused questions are most similar to Reading Comprehension questions, but can require analysis of tabular data in order to answer the question. The sample math-focused questions deal primarily with budgets and costs, but can include other math concepts such as percents and rates.

About 2/3 of the sample MSR questions are 3-part opposite-answer questions and about 1/3 are traditional multiple-choice questions. Note that a minority of the sample math-focused questions are 3-part questions, whereas almost 4/5 of the sample verbal-focused questions are 3-part. With 3-part questions, we find that all three parts have the same answer infrequently. If you get the same answer for all three parts, quickly ensure that you have not erred (the same holds true for Table Analysis). Likewise, if you are unsure about one of the three sub-questions and you get the same answer for the other two sub-questions, you should guess the opposite answer for the sub-question that you are unsure about.

May 24 2013

Flawed IR Two-Part Analysis Questions

I have worked through thousands of official GMAC math and verbal questions, from GMATPrep and from the Official Guides going all the way back to the Third Edition from 1986. In all these questions, I have not found a single incorrect answer. Although there has been a rare verbal question with a debatable answer, I have never felt that any answer was truly wrong. This is why it troubles me that GMAT Genius has found two different half-baked Two-Part Analysis Integrated Reasoning questions, both in the online Integrated Reasoning component of the Official Guide (13th Edition). After multiple reviews, I remain convinced that both of these questions are flawed.

I am surprised that these two Two-Part Analysis IR questions do not live up to the standards of rigor and excellence that the GMAC is known for. Because the questions are part of the Official Guide, which was released before the Integrated Reasoning section launched, these two questions never appeared as real GMAT questions. As a result, these questions may not have been thoroughly tested with actual test takers. But that does not excuse the GMAC for allowing sloppy questions into its study guide. We can only hope that live Integrated Reasoning questions on the real GMAT will have received a much higher level of rigor and scrutiny, so that student IR scores are not unjustly impacted due to similarly negligent questions.

You may wonder why GMAT Genius has come across this only now. Honestly, we haven’t paid too much attention so far to Integrated Reasoning. Since this is a relatively new section, we believe that business schools won’t place much weight on IR in the near term. As we approach Integrated Reasoning’s one year birthday on June 5, however, we felt that IR deserved a closer look. We therefore decided to carefully evaluate all 105 official IR questions that the GMAC has made available for practice. It is worth noting that the other 103 IR questions that we evaluated are perfectly fine. Although a flaw rate of less than 2% would actually be good for some companies, this is a total shocker by the GMAC’s standards. My next post will detail some observations that we made from our analysis of the 105 IR questions.

Be forewarned that I will now be discussing in extensive detail the two flawed Official Guide IR questions. The details that follow may not make sense unless you have read these questions. You may wish to try these two questions on your own first, using your OG access to IR questions, before viewing the screenshots and discussion. Clicking the thumbnail of a screenshot below will bring up a full-size image of the question along with the official explanation.

IR Question #37

Official Guide Two-Part Analysis Integrated Reasoning Question #37This question pertains to various causes for the decline of coral reefs. One definite factor is a type of sea star that eats coral. Human fishing has reduced the sea star’s predators. This clearly implies that there are now more sea stars, and therefore more coral consumption by sea stars. A second possible cause is that a runoff has resulted in greater phytoplankton blooms, and we are told that the sea star happily eats phytoplankton. Our task is to pick a cause-and-effect sequence that probably results in coral decline.

The correct answer to this IR question is that an increase in phytoplankton (cause) resulted in an increase of sea stars (effect). How would a non-biologist know that eating phytoplankton causes an increase of sea stars? Just because an organism gladly eats something doesn’t necessarily mean that the organism reproduces more rapidly. This is akin to saying that when people eat pizza, the world population increases. This analogy shows the absurdity in the purportedly correct cause-and-effect sequence.

GMAT questions expect us to make reasonable inferences from the information provided in the stimulus. But we are not expected to possess any specialized outside knowledge (such as the definition of phytoplankton) in order to correctly answer a question. So what could be a reasonable inference here? In my interpretation, I guessed that phytoplankton blooms on or near coral, and since the sea star enjoys eating phytoplankton, coral reef decline inevitably occurs.

Part of the problem lies in the wording of the stimulus. The first sentence tells us that various causes are at hand. So this is not a debate between two distinct causes (i.e. one OR the other). Furthermore, we already know that a lack of predators has led to an increase in sea stars, so it is not necessary to justify an increase in sea stars. Admittedly this IR question does not contain any other satisfactory answer other than the credited response. But the correct answer would be more understandable if the question stated that only one of the two mentioned causes can be correct. In that case, it would be necessary to explain an increase in sea stars. As worded, however, the leap-of-faith required to pick the correct answer goes significantly beyond a reasonable inference.

IR Question #50

Official Guide Two-Part Analysis Integrated Reasoning Question #50This question is about a mattress company with one store in City X and one store in City Z. Pretty much everything about the two stores and cities is the same, except that the mattress store in City Z conducts twice as much radio advertising as the City X store. A consultant claims that the radio advertising has not benefitted sales, and we must decide upon what changes we could make in Cities X and Z to test this hypothesis.

Unfortunately the correct answer, eliminate radio advertising in both cities, fails to test the hypothesis. Why? As we see in several GMAT Critical Reasoning questions, we need a control group to accurately carry out a test. We should have two groups that are identical except for in the one variable that we are testing. Without a control group, we cannot be confident about the true cause of an effect that we observe. In this specific question, let’s suppose that we eliminate radio advertising in both cities and sales in both cities subsequently decline. How do we know whether the sales decline is due to the lack of radio advertising or due to another factor, such as seasonality or an economic slump? Without a control group, we cannot isolate the true cause.

On the other hand, if we eliminate radio advertising in only one city but keep it in the other city, then we could compare the impact to sales. If sales declines in both cities, then clearly another factor (such as an economic slump) came into play. If sales declines in only the city with no radio advertising, then clearly radio advertising does have an impact on sales. Finally, if sales do not decline in either city, then the consultant’s hypothesis is correct. Only with a control group can we truly evaluate cause-and-effect. The GMAC’s answer to this IR question is undoubtedly wrong.

Do you agree or disagree? Feel free to let us know by submitting a comment.

May 05 2013

Just Like a Rock Star?

The Fresh Beat BandThose of you preparing for the GMAT are too old to be fans of The Fresh Beat Band, a rock band of four high school students as depicted on a popular Nickelodeon TV show. Let’s be thankful for that, as you won’t risk learning bad grammar. In one of its popular songs / videos, Just Like a Rock Star, the band exhorts listeners to “Shout it out, just like a rock star.” This brings up a common Sentence Correction idiomatic issue: “as” versus “like” in answer choices.

The word “like” is specifically used to compare two nouns. For example, we could say that a giraffe’s neck is like that of a brachiosaurus. The word “as” is specifically used to compare two actions, and it’s usage in this manner often requires a form of the verb “to do” in the second part of the comparison. For example, we may claim that a giraffe plods slowly along as a brachiosaurus did in its time. We should not, however, write that a giraffe plods slowly along like a brachiosaurus. In this incorrect version, we are comparing the giraffe’s action (of plodding along) to the actual dinosaur, not to the dinosaur’s style of moving.

Furthermore, the word “just” in a comparison usage takes on the meaning “exactly.” Thus “just like” implies “exactly like,” a meaning that is unlikely to be accurate. As a result, the GMAT highly prefers comparisons that use “as” or “like” without a preceding “just.”

So if The Fresh Beat Band were to be grammatically correct, the song’s lyrics would be “Shout it out, as a rock star does.” Admittedly this doesn’t sound nearly as jazzy in a song. But it would earn the band members a higher score on the GMAT. In real life, we frequently find prose that breaks the strict grammatical requirements of the GMAT. But for those of you wanting to achieve a “rock star” performance on the GMAT, keep in mind the GMAT’s strict rules of usage.

May 03 2013

Introducing Our New Website

GMAT Genius LogoWelcome to GMAT Genius! Our objective is to help you achieve your highest potential on the GMAT. We are proud to introduce our new website, which incorporates a blog and social media. Through these channels, we intend to provide you with useful articles and advice that will help you learn about and prepare for the GMAT and business school.

On our main website, you will find the most extensive free preparation advice. We also offer private GMAT tutoring in Irvine and Tustin, California, with our Chief Genius, one of the most skilled and experienced GMAT instructors in the industry. Later this year, we will be introducing an online shopping cart plus two additional service offerings. Stay tuned.

We’d love for you to spread the word about GMAT Genius. Please also feel free to contact us with any questions or suggestions. We look forward to helping you achieve GMAT success!