Jun 20 2017

2018 GMAT Official Guide – Detailed Analysis / Question Categorization

2018 GMAT Official GuideGMAT Genius has thoroughly analyzed the 2018 GMAT Official Guide and we want to share our insights with you. Feel free to read our detailed analysis of the 2018 GMAT Official Guide or skip down to our conclusions. Wishing you tremendous success with the GMAT!

Overview of 2018 GMAT Official Guide

The Official Guides for GMAT Review contain retired real GMAT questions, and are an essential component of your GMAT preparations. The GMAC places questions in order of increasing difficulty, based on its assessment of difficulty. This book has no overlap in practice questions with the Quant and Verbal Official Guides.

The 2018 GMAT Official Guide contains 130 new questions out of the 957 total questions (including Integrated Reasoning). Excluding the 100 questions in the Diagnostic Exam section of the book, the new questions represent just over 15% new content. These are new questions that we have not encountered before; they are not questions recycled from older GMAC resources.

Problem Solving

The 2018 GMAT Official Guide contains 254 Problem Solving questions, including the 24 Problem Solving questions in the Diagnostic Exam portion of the book. The GMAC classifies question difficulty into three categories as follows:

Difficulty Number Percent Change
Easy 96 38% +14
Medium 59 23% +4
Hard 99 39% (18)

The Problem Solving section contains 35 new questions, with difficulty of Easy / Medium / Hard as follows: 22 / 7 / 6. This is in lieu of 35 questions from the 2017 edition that have been removed, with difficulty of Easy / Medium / Hard as follows: 8 / 3 / 24. Unlike in prior years, the GMAC has not reclassified the difficulty of any question.

GMAT Genius classifies question difficulty into five categories. Our assessment of this section skews significantly easier, and contains notable differences from the GMAC’s assessment. Our difficulty assessment is only 69.9% correlated with the GMAC’s assessment, demonstrating tremendous subjectivity involved in assessing question difficulty. Here’s our breakdown:

Difficulty Number Percent Change
Super Easy 23 9% +3
Easy 70 28% +2
Medium 104 41% (5)
Hard 38 15% (2)
Very Hard 19 7% +2

Although math questions often entail multiple math concepts, GMAT Genius classifies questions based on our assessment of the primary math concept. We break down the 254 Problem Solving questions as follows:

Type Concept Number Percent Change
Arithmetic Basic 10 3.9% +3
Arithmetic Absolute Value 4 1.6%
Arithmetic Divisibility/Factors/Mult. 17 6.7% +2
Arithmetic Exponents & Roots 18 7.1% (4)
Arithmetic Fractions & Ratios 28 11% (2)
Arithmetic Percents 20 7.9%
Arithmetic Pos/Neg & Odd/Even 1 0.4%
Arithmetic Primes 4 1.6%
Algebra Inequalities 5 2%
Algebra Linear Equations 14 5.5% +1
Algebra Quadratics 8 3.1%
Algebra Simultaneous Equations 7 2.8%
Algebra Variables in Answers 8 3.1% +1
Geometry Circles 4 1.6% (1)
Geometry Coordinate 7 2.8% (1)
Geometry Rectangles 7 2.8%
Geometry Triangles 8 3.1% +2
Geometry Other 7 2.8%
Statistics Averages 18 7.1% (1)
Statistics Other 7 2.8% +1
Word Problems Combinatorics 7 2.8%
Word Problems Functions & Sequences 10 3.9% (1)
Word Problems Groups/Sets 7 2.8%
Word Problems Probability 7 2.8% (1)
Word Problems Revenue/Profit/Interest 9 3.5% +1
Word Problems Rate & Work 12 4.7%

Here’s a list of the 35 new Problem Solving questions:
3, 5, 6, 16, 22, 23, 24, 26, 33, 34, 40, 42, 50, 53, 55, 60, 68, 69, 72, 79, 81, 85, 90, 96, 98, 104, 122, 125, 139, 140, 151, 173, 201, 224, 229

Here’s a list of the 230 Problem Solving questions, excluding those in the Diagnostic Exam, categorized by primary math concept:

Type Concept Question #s
Arithmetic Basic 2, 19, 22, 37, 46, 79, 157, 173, 219
Arithmetic Absolute Value 25, 27, 65, 193
Arithmetic Divisibility/Factors/Mult. 33, 44, 54, 73, 81, 98, 121, 126, 136, 141, 154, 175, 176, 178, 195
Arithmetic Exponents & Roots 66, 68, 71, 74, 90, 92, 112, 147, 161, 180, 200, 209, 213, 216, 223, 230
Arithmetic Fractions & Ratios 3, 4, 5, 28, 30, 36, 45, 59, 63, 72, 75, 82, 91, 97, 103, 124, 131, 133, 135, 139, 160, 163, 189, 192, 203, 220, 222
Arithmetic Percents 1, 6, 10, 15, 55, 70, 80, 86, 87, 89, 94, 106, 108, 119, 122, 125, 153, 169, 172, 207
Arithmetic Pos/Neg & Odd/Even 62
Arithmetic Primes 181, 205
Algebra Inequalities 49, 78, 117, 185, 228
Algebra Linear Equations 7, 12, 31, 42, 53, 67, 83, 85, 109, 111, 128, 134, 179, 184
Algebra Quadratics 51, 93, 110, 127, 155, 168, 188, 226
Algebra Simultaneous Equations 13, 20, 35, 100, 150, 186
Algebra Variables in Answers 9, 16, 48, 57, 61, 144, 167, 190
Geometry Circles 95, 123, 146, 177
Geometry Coordinate 50, 56, 77, 101, 107, 183, 218
Geometry Rectangles 17, 18, 39, 58, 99, 156, 202
Geometry Triangles 26, 29, 43, 145, 174, 224
Geometry Other 32, 34, 114, 159
Statistics Averages 14, 21, 40, 41, 96, 116, 137, 138, 149, 158, 164, 171, 194, 211, 217, 227
Statistics Other 52, 84, 115, 151, 166, 197, 204
Word Problems Combinatorics 140, 148, 182, 187, 201, 214
Word Problems Functions & Sequences 47, 88, 104, 165, 196, 198, 206, 212, 225
Word Problems Groups/Sets 118, 120, 152, 208, 229
Word Problems Probability 11, 142, 162, 170, 221
Word Problems Revenue/Profit/Interest 24, 38, 60, 130, 143, 191, 210, 215
Word Problems Rate & Work 8, 23, 64, 69, 76, 102, 105, 113, 129, 132, 199

Data Sufficiency

The 2018 GMAT Official Guide contains 198 Data Sufficiency questions, including the 24 Data Sufficiency questions in the Diagnostic Exam portion of the book. The GMAC classifies question difficulty into three categories as follows:

Difficulty Number Percent Change
Easy 58 29% +8
Medium 57 29% +6
Hard 83 42% (14)

The Data Sufficiency section contains 26 new questions, with difficulty of Easy / Medium / Hard as follows: 11 / 10 / 5. This is in lieu of 26 questions from the 2017 edition that have been removed, with difficulty of Easy / Medium / Hard as follows: 3 / 4 / 19. The GMAC has not reclassified the difficulty of any question.

GMAT Genius classifies question difficulty into five categories. Our assessment skews significantly easier, and contains notable differences from the GMAC’s assessment. Our difficulty assessment is only 56.0% correlated with the GMAC’s assessment, demonstrating tremendous subjectivity involved in assessing question difficulty. Here’s our breakdown:

Difficulty Number Percent Change
Super Easy 9 5% +2
Easy 58 29% +8
Medium 90 45% (2)
Hard 35 18% (6)
Very Hard 6 3% (2)

Although many math questions entail multiple math concepts, GMAT Genius classifies questions based on our assessment of the primary math concept. We break down the 198 Data Sufficiency questions as follows:

Type Concept Number Percent Change
Arithmetic Basic 17 8.6% +7
Arithmetic Divisibility/Factors/Mult. 9 4.5% +1
Arithmetic Exponents & Roots 14 7.1%
Arithmetic Fractions & Ratios 11 5.6% (2)
Arithmetic Percents 15 7.6% (1)
Arithmetic Pos/Neg & Odd/Even 8 4% (1)
Arithmetic Primes 1 0.5%
Algebra Inequalities 14 7.1% +4
Algebra Linear Equations 11 5.6% +1
Algebra Quadratics 3 1.5% (1)
Algebra Simultaneous Equations 9 4.5% (1)
Geometry Circles 5 2.5%
Geometry Coordinate 7 3.5%
Geometry Rectangles 4 2%
Geometry Triangles 10 5.1%
Geometry Other 5 2.5% (1)
Statistics Averages 14 7.1%
Statistics Other 10 5.1% (1)
Word Problems Functions & Sequences 4 2% (1)
Word Problems Groups/Sets 11 5.6%
Word Problems Probability 3 1.5%
Word Problems Revenue/Profit/Interest 6 3% (2)
Word Problems Rate & Work 7 3.5% (2)

Here’s a list of the 26 new Data Sufficiency questions:
233, 258, 260, 262, 266, 267, 273, 274, 276, 277, 278, 282, 284, 287, 288, 292, 293, 300, 306, 313, 326, 334, 339, 376, 382, 391

Here’s a list of the 174 Data Sufficiency questions, excluding those in the Diagnostic Exam, categorized by primary math concept:

Type Concept Question #s
Arithmetic Basic 258, 262, 270, 273, 283, 284, 288, 292, 309, 326, 329, 333, 334, 349, 372, 388, 403
Arithmetic Divisibility/Factors/Mult. 285, 293, 328, 337, 356, 390
Arithmetic Exponents & Roots 240, 243, 249, 281, 289, 330, 342, 350, 365, 370, 399
Arithmetic Fractions & Ratios 233, 256, 275, 312, 325, 335, 354, 368, 387, 402, 404
Arithmetic Percents 239, 253, 259, 269, 286, 313, 318, 319, 321, 324, 332, 340, 362, 397
Arithmetic Pos/Neg & Odd/Even 255, 271, 277, 278, 308, 314, 344
Arithmetic Primes 357
Algebra Inequalities 246, 274, 291, 306, 315, 320, 338, 355, 359, 361, 376, 391, 401
Algebra Linear Equations 234, 247, 252, 280, 290, 310, 339, 351, 352
Algebra Quadratics 279, 323, 366
Algebra Simultaneous Equations 232, 245, 303, 307, 322, 327, 345, 360
Geometry Circles 263, 287, 369, 379
Geometry Coordinate 235, 264, 331, 347, 382, 383
Geometry Rectangles 301, 311, 367
Geometry Triangles 231, 237, 260, 265, 346, 353, 384, 386, 398
Geometry Other 261, 304, 343, 371, 400
Statistics Averages 282, 295, 300, 348, 358, 363, 373, 375, 378, 381, 392, 396
Statistics Other 242, 244, 298, 317, 336, 385, 394, 395
Word Problems Functions & Sequences 241, 257, 364, 377
Word Problems Groups/Sets 248, 254, 266, 267, 276, 294, 305, 316, 389
Word Problems Probability 236, 297, 302
Word Problems Revenue/Profit/Interest 250, 268, 272, 296, 393
Word Problems Rate & Work 238, 251, 299, 341, 374, 380

Sentence Correction

The 2018 GMAT Official Guide contains 158 Sentence Correction questions, including the 18 Sentence Correction questions in the Diagnostic Exam portion of the book. The GMAC classifies question difficulty into three categories as follows:

Difficulty Number Percent Change
Easy 36 23% +1
Medium 49 31% (1)
Hard 73 46%

The Sentence Correction section contains 21 new questions, with difficulty of Easy / Medium / Hard as follows: 4 / 4 / 13. This is in lieu of 21 questions from the 2017 edition that have been removed, with difficulty of Easy / Medium / Hard as follows: 3 / 5 / 13. The GMAC has not reclassified the difficulty of any question.

GMAT Genius classifies question difficulty into five categories. Our assessment skews noticeably easier, and contains notable differences from the GMAC. Our difficulty assessment is only 56.8% correlated with the GMAC’s assessment, clearly showing that there is subjectivity involved in assessing question difficulty. Here’s our breakdown:

Difficulty Number Percent Change
Super Easy 3 2%
Easy 43 27% (1)
Medium 67 42% (3)
Hard 38 24% +4
Very Hard 7 4%

Although Sentence Correction questions typically entail multiple grammar concepts (as described on our website), GMAT Genius classifies questions based on our assessment of the primary tested concept. We classify the 158 Sentence Correction questions as follows:

Concept Number Percent Change
Verb Agreement 19 12% +1
Verb Tense 22 13.9%
Pronoun Ambiguity 12 7.6% +2
Pronoun Agreement 4 2.5%
Parallel Construction 50 31.6% (2)
Misplaced Modifiers 16 10.1% (1)
Idioms 8 5.1% +1
Comparison & Quantity 10 6.3% (1)
Expression & Meaning 17 10.8%

Here’s a list of the 21 new Sentence Correction questions:
674, 680, 684, 685, 699, 702, 717, 735, 743, 745, 750, 751, 763, 770, 777, 780, 781, 782, 784, 796, 799

Here’s a list of the 140 Sentence Correction questions, excluding those in the Diagnostic Exam, categorized by primary grammar concept:

Concept Question #s
Verb Agreement 670, 677, 685, 693, 707, 711, 721, 752, 753, 759, 771, 789, 792, 793, 799, 801, 807
Verb Tense 668, 686, 694, 701, 702, 708, 712, 722, 724, 731, 735, 740, 749, 754, 756, 764, 773, 781, 803, 804
Pronoun Ambiguity 671, 719, 743, 774, 775, 777, 778, 779
Pronoun Agreement 688, 738, 762, 765
Parallel Construction 669, 679, 680, 682, 687, 689, 692, 697, 699, 703, 710, 713, 714, 715, 725, 727, 728, 730, 732, 734, 736, 737, 741, 742, 744, 751, 755, 757, 760, 761, 763, 766, 767, 776, 780, 782, 783, 784, 794, 800, 802, 806
Misplaced Modifiers 683, 705, 706, 709, 716, 718, 723, 729, 739, 746, 748, 770, 790, 797, 798
Idioms 672, 695, 698, 717, 788, 795, 796
Comparison & Quantity 676, 678, 691, 704, 745, 758, 769, 772, 791, 805
Expression & Meaning 673, 674, 675, 681, 684, 690, 696, 700, 720, 726, 733, 747, 750, 768, 785, 786, 787

Critical Reasoning

The 2018 GMAT Official Guide contains 141 Critical Reasoning questions, including the 17 Critical Reasoning questions in the Diagnostic Exam portion of the book. The GMAC classifies question difficulty into three categories as follows:

Difficulty Number Percent Change
Easy 41 29%
Medium 44 31% (1)
Hard 56 40% +1

The Critical Reasoning section contains 19 new questions, with difficulty of Easy / Medium / Hard as follows: 6 / 2 / 11. This is in lieu of 19 questions from the 2017 edition that have been removed, with difficulty of Easy / Medium / Hard as follows: 6 / 3 / 10. The GMAC has not reclassified the difficulty of any question.

GMAT Genius classifies question difficulty into five categories. Our assessment skews slightly easier, but contains notable differences from the GMAC. Our difficulty assessment is 74.1% correlated with the GMAC’s assessment, clearly indicating subjectivity involved in assessing question difficulty. Here’s our breakdown:

Difficulty Number Percent Change
Super Easy 0 0%
Easy 43 30% (2)
Medium 49 35% (1)
Hard 36 26% +3
Very Hard 13 9%

We have grouped the questions based on the question type categorization that GMAT Genius uses for Critical Reasoning (as described on our website). We break down the 141 Critical Reasoning questions as follows:

Concept Number Percent Change
Weaken 29 20.6% +2
Strengthen 27 19.1% (2)
Assumption 15 10.6% +1
Reasoning 4 2.8% (1)
Conclusion 9 6.4%
Explain 18 12.8% +1
Evaluate 15 10.6% (1)
Boldface 9 6.4%
Complete the Passage 15 10.6%

Here’s a list of the 19 new Critical Reasoning questions:
546, 550, 554, 556, 561, 575, 589, 599, 626, 627, 631, 634, 635, 640, 643, 651, 656, 660, 661

Here’s a list of the 124 Critical Reasoning questions, excluding those in the Diagnostic Exam, categorized by CR question type:

Concept Question #s
Weaken 546, 549, 574, 575, 583, 588, 600, 606, 615, 617, 619, 620, 622, 625, 627, 629, 642, 646, 654, 658, 664, 666, 667
Strengthen 545, 547, 548, 552, 562, 566, 569, 570, 572, 576, 589, 592, 594, 595, 597, 598, 602, 604, 610, 611, 624, 631, 641, 648, 649
Assumption 555, 580, 584, 590, 607, 608, 614, 628, 635, 637, 645, 650, 655, 657
Reasoning 560, 567, 578, 633
Conclusion 544, 581, 591, 618, 634, 653, 662
Explain 551, 553, 556, 557, 558, 568, 586, 596, 613, 616, 621, 630, 640, 656, 660, 665
Evaluate 554, 559, 571, 573, 579, 585, 632, 636, 638, 643, 644, 663
Boldface 561, 565, 599, 623, 639, 647, 651, 652, 659
Complete the Passage 550, 563, 564, 577, 582, 587, 593, 601, 603, 605, 609, 612, 626, 661

Reading Comprehension

The 2018 GMAT Official Guide contains 156 Reading Comprehension questions across 33 passages, including the 17 Reading Comprehension questions in 3 passages in the Diagnostic Exam portion of the book. The GMAC classifies question difficulty into three categories as follows:

Difficulty Number Percent Change
Easy 55 35% +4
Medium 74 47% +1
Hard 27 17% (5)

In the Reading Comprehension section, questions are not fully presented in order of progressive difficulty, contrary to what the back cover of the book claims. Based on difficulty levels provided in the online version, Easy, Medium, and Hard difficulty questions are interspersed. The following table shows the question numbers for each difficulty level:

Difficulty Question #s
Easy 405-438, 442-455
Medium 439-441, 456-516, 537-540
Hard 517-536, 541-543

The Reading Comprehension section contains 21 new questions in 6 passages, with difficulty of Easy / Medium / Hard as follows: 7 / 14 / 0. This is in lieu of 21 questions in 4 passages from the 2017 edition that have been removed, with difficulty of Easy / Medium / Hard as follows: 3 / 13 / 5. The GMAC has not reclassified the difficulty of any question.

GMAT Genius classifies question difficulty into five categories. Whereas the GMAC assigns the same difficulty to all questions for a given passage (except in the Diagnostic Exam section), GMAT Genius assesses the difficulty of each question individually. Our assessment skews slightly harder, but contains notable differences from the GMAC. Our difficulty assessment is only 57.6% correlated with the GMAC’s assessment, in large part due to different difficulty assessment methodologies. Here’s our breakdown:

Difficulty Number Percent Change
Super Easy 7 4% +1
Easy 33 21%
Medium 65 42% (2)
Hard 41 26% +1
Very Hard 10 6%

We have grouped the questions based on the question type categorization that GMAT Genius uses for Reading Comprehension (as described on our website). We break down the 156 Reading Comprehension questions as follows:

Concept Number Percent Change
Primary Purpose 22 14.1% (2)
Author’s Tone 10 6.4%
Organization 5 3.2% +1
Function 20 12.8% +2
Specific Reference 38 24.4%
Inference 47 30.1% (3)
Critical Reasoning 14 9% +2

Here’s a list of the 21 new Reading Comprehension questions: 412 to 418, 439 to 441, 467 to 470, 514 to 516, 537 to 540

We have not provided a list of Reading Comprehension questions by category because it makes sense to practice on one passage at a time, rather than attempting all the Primary Purpose questions (for example) at one go.

Integrated Reasoning

The 2018 GMAT Official Guide includes online access to 58 Integrated Reasoning practice questions. The IR set includes 8 new questions that we have not seen before, plus all 50 questions from the prior 2017 edition. The 58 questions consist of the following four types:
Multi-Source Reasoning – 21 (3 new)
Table Analysis – 7 (1 new)
Graphics Interpretation – 12 (2 new)
Two-Part Analysis – 18 (2 new)

The GMAC classifies question difficulty into three categories of Easy / Medium / Hard as follows:
Multi-Source Reasoning – 6 / 7 / 8
Table Analysis – 3 / 1 / 3
Graphics Interpretation – 4 / 3 / 5
Two-Part Analysis – 5 / 7 / 6
Total – 18 / 18 / 22

Out of the 50 questions that carry over from the 2017 edition, the GMAC has reclassified the difficulty of 33 questions. For IR, GMAT Genius classifies question difficulty into the same three categories. Except for Two-Part Analysis, our assessment skews significantly easier, and contains notable differences from the GMAC. Our difficulty assessment is only 8.1% correlated with the GMAC’s assessment, clearly showing that there is tremendous subjectivity involved in assessing question difficulty. Here’s our breakdown of Easy / Medium / Hard:
Multi-Source Reasoning – 9 / 11 / 1
Table Analysis – 3 / 4 / 0
Graphics Interpretation – 3 / 7 / 2
Two-Part Analysis – 2 / 10 / 6
Total – 17 / 32 / 9

Online Interface

2018 GMAT Official Guide Online InterfaceThe 2018 GMAT Official Guide includes an access code (see inside front cover) that provides 12-month usage of an online version of this Official Guide. The online practice interface is the same as it was previously, except that the onerous limit of 10 saved sessions has been increased to 25 saved sessions in Exam Mode plus 25 saved sessions in Practice Mode (which you should not use, as mentioned below). The 100 questions from the Diagnostic Test chapter are available in a separate tab that works with Exam Mode functionality.

Since the GMAT is a computer-based test, we believe that it is advisable to work though the questions online. We strongly suggest that you use Exam Mode rather than Practice Mode, since we recommend that students practice using timed question sets that replicate test day conditions. The functionality of the online platform is good overall. You can choose practice sets by question type and difficulty level. Every question lists the corresponding book question number for easy cross-referencing.

Other Notes

The Official Guides are for practicing with real GMAT questions, not for learning the underlying concepts. The book contains a 40-page Math Review section that provides a very high-level overview of the math concepts tested on the GMAT. This math review will be highly inadequate except perhaps for the most advanced math students. Similarly, the brief introductions to the concepts tested on the verbal section are highly inadequate. We recommend that you use additional study materials to learn the math and verbal concepts.

Although all questions include answer explanations, many GMAT test takers are far from satisfied with these explanations. Math explanations can be brief and hard-to-understand for non-advanced students, and are sometimes convoluted or inefficient. Most GMAT test takers consider the Sentence Correction explanations quite cryptic. The Critical Reasoning and Reading Comprehension explanations, however, are reasonably good overall.

Conclusions

The 2018 GMAT Official Guide has three primary weaknesses, in our opinion:

  1. An insufficient amount of difficult practice questions, particularly based on GMAT Genius’ assessment of difficulty. We are especially dismayed to see the net loss of 32 Hard-difficulty Quant questions (18 Problem Solving and 14 Data Sufficiency) based on GMAC’s difficulty assessment compared to the 2017 edition.
  2. Math answer explanations that are too often either brief or convoluted and Sentence Correction explanations that are too cryptic.
  3. In the Reading Comprehension section, questions are not fully presented in order of progressive difficulty, contrary to what the back cover of the book claims.

Despite these flaws, the 2018 GMAT Official Guide is an essential source of GMAT practice. We believe that every GMAT aspirant must use this book (or the prior edition). For the best value, we recommend purchasing this book as part of 2018 GMAT Official Guide Bundle. If you already have the 2017 edition of this book, however, the replacement of 61 math questions and 61 verbal questions is not sufficient to make this edition worth purchasing.

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