Yeah I think one of the reasons could be that GMATPrep does not contain experimental questions as GMAT does.

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You may refer to the gmat pacer from the below link:

verbal-chat-this-wednesday-feb-13th-9-a-m-pst-147125.html#p1181996

Vercules

Hi vercules
I may sound silly ...but i hav a doubt...
I know that test centre ppl give only one note book for rough work.......where should i write the timing of the pacer ...I have been practising by writing it in a paper and keeping infront of the desktop...do the test center ppl will give 2 notebooks for rough work intially....i do not think so


what is the soln to this


Archit

GMAT Prep Software Analysis and What If Scenarios

We will try to run different scenarios with GMAT Prep Software to find out whether various myth about scoring algorithm are legit.

Reports from the Real GMAT:

Added a few points to my verbal score: 600-to-740-all-about-timing-and-fundamentals-147029.html

1. What is the importance of the first 10 questions?

Experiment: We will try to disprove the myth the way OG/GMAC positions it: the first 10 questions are not critical
Methodology: we will attempt the worst case scenario and will answer the first 10 questions incorrectly (not guess but incorrectly); then we will attempt to answer the first 27 questions correctly and then the last 10 incorrectly (not guess)
Results: Q38 (48th percentile - ouch) with only 10 wrong answers
Analysis: obviously something is not right with the myth about the first 10 questions. They appear to be very important on the Quant. If you miss the first 10 (probably not a very realistic scenario for most) you have no way of climbing out of the hole - almost all questions that were offered to me were generally easy/medium difficulty. Let's try a different scenario next to check this myth (we'll miss the last 10 questions). Also interesting to note, when simulated in the previous GMAT Prep version, this scenario resulted in Q41 (so there have been changes in the scoring algorithms of the GMAT Prep).
Total Score: every question in the verbal section was answered as "E" and it resulted in the final score of V8, 1st percentile. Total score: 380 - 10th percentile
Questions: 20PS and 17 DS. Also, see what question topics were encountered in this scenario:

2. What is the importance of the last 10 questions?

Experiment: We will try to analyze the importance of the last 10 questions and if it equals the important of the first 10
Methodology: we will attempt the worst case scenario and will answer the first 27 Q questions correctly and then will answer the remaining 10 questions incorrectly (not guess but incorrectly).
Results: Q50, 92nd percentile - Nicely done though not great. I think it is possible to get Q51 with 10 incorrect ones.
Analysis: The questions were much harder this time with some new topics/types appearing on the test such as coordinate geometry DS. Conclusion: the last 10 don't count as much as the first 10. This myth is True (as long as you can get the first 27 right). Please note that I have not guessed the last 10 but rather answered them incorrectly (which means I still had to solve those questions too). If you are guessing, you will most likely get a higher score.
Total Score: every question in the verbal section was answered as "E" (again) and it resulted in the final score of V8, 1st percentile. Total score: 470 (90 points higher than when we missed the first 10 questions)
Questions: 20PS and 17 DS. Also, see what question topics were encountered in this scenario:

3. What is the importance of the middle 10 questions?

Experiment: We will try to analyze the importance of the middle 10 questions and see how it compares to the results of the previous 2 experiments
Methodology: we will attempt the worst case scenario and will answer the first 14 Q questions correctly; then I will answer incorrectly the following 10 questions, and will answer the remaining 13 questions correctly.
Results: Q49, 85th percentile - not as good of a result as in the case of missing the last 10 questions but it was much less effort (fewer hard questions than in the second case)
Analysis: The questions were not much easier than in the second scenario above even though I have made 10 consecutive mistakes. So, it may be a slightly better value in terms of effort/score but not by far
Total Score: every question in the verbal section was answered as "D" this time and it resulted in the final score of V6, 1st percentile. (Interestingly enough, it was a slightly worse result than "E"). Total score: 450

4. What is the penalty if I miss every third question?

Experiment: I will try to test a scenario in which a test takers answers every third question incorrectly (e.g. 3, 6, 9, etc. Thus giving themselves an extra 2 mins on quant). This scenario will simulate someone who takes 3 mins instead of 2 per question and then guesses every third question. Please note that this is the worst case scenario (we do not get any guesses right)
Methodology: Every 3rd questions answered incorrectly. So, 13 incorrect and 24 correct answers.
Results: Q49, 85th percentile
Analysis: Slightly lower score than in the case of missing the last 10 questions but it was much less effort in getting here(fewer hard questions than in the second or third scenarios I have tested). So far this is the best value in terms of effort/final score
Total Score: This time every question in the verbal section was answered as "C" this time and it resulted in the final score of V8, 1st percentile. Total score: 460, 23rd percentile.

5. Best Guessing Strategy: Part I - What if we guess a bunch of questions in the middle?

Experiment: I will attempt 3 different scenarios that will examine guessing strategies to figure out where the time should be invested.
Methodology: First 10 questions answered correctly, then GUESSED the next 17 questions (answered C to all of them and got 4 out of 17 correct) and finally answered the remaining 10 questions correctly.
Results: Q46, 73rd percentile.
Analysis: This is a pretty similar to the scenario above where we tried to figure out the importance of the middle 10 questions; missing 3 more (13 wrong vs 10 wrong) resulted in a lower score by 3 points (46 vs. 49).
Total Score: Every question in the verbal section was answered as "B" this time and it resulted in the final score of V6, 0 percentile. Total score: 420, 16th percentile.
Questions: 21PS and 16 DS.

6. Best Guessing Strategy: Part II - guess every third question

Experiment: I will try to test a scenario in which a test takers GUESSES every other question (e.g. 2, 4, 6, etc). I was answering C to all even numbered question and guessed correctly 3 out of 18
Results: Q40, 55th percentile. (22 correct answers and 15 incorrect answers, I guessed 3 questions correctly.)
Analysis: Not sure what I was expecting guessing every other question. I guess I got the 55th percentile (half the ultimate score but I also only invested half the effort and gottend double the time to answer my other questions). So far, I don' think this is the best strategy in terms of guessing since my goal would be to get the most return for the least amount of effort. However, I do think this score is too low to be seriously considered by anyone.
Total Score: Every question in the verbal section was answered as "A" this time and it resulted in the final score of V6, 0 percentile. Total score: 380, 10th percentile.

7. Best Guessing Strategy Part III - Variable Guessing

Experiment: first 10 questions answered correctly, GUESSED the next 9 questions (answered C to all of them, guessed 2 out of 9), then answered the next 9 questions correctly and finally GUESSED the remaining 9 questions (answered C to all of them, guessed 2 out of 9). So, 23 correct, 14 incorrect.
Results: Q49, 85th percentile. (23 correct answers and 14 incorrect answers, I guessed 3 questions correctly.)
Analysis: I was amazed to see Q49 as my final score. So far I think this is the best guessing strategy. It has resulted into the highest score (49) with 14 incorrect answers (compare that to scenario #5 above where I guessed the 17 middle questions and gotten 4 of them correct. I made 13 mistakes mistakes on that test but the final score was only 46. In this scenario I still only solved half the questions (guessed the other half). However, that's pretty darn good for solving only half the questions.
Total Score: Every question in the verbal section was answered as "E" and it resulted in the final score of V9, 2 percentile. Total score: 470, 26th percentile.

8. PS vs DS: what is the importance of DS questions?

Experiment: first 10 questions answered correctly. After that, I answered incorrectly to 12 DS questions only. So, 25 correct and 12 incorrect answers (all DS).
Results: Q50, 92th percentile.
Analysis:
Total Score: Every question in the verbal section was answered as "E" and it resulted in the final score of V8, 1 percentile. Total score: 470, 26th percentile.

9. PS vs DS: what is the importance of PS questions?

Experiment: first 10 questions answered correctly. After that, I answered incorrectly to 12 PS questions only. So, 25 correct and 12 incorrect answers (all PS).
Results: Q49, 85th percentile.
Analysis:
Total Score: Every question in the verbal section was answered as "E" and it resulted in the final score of V11, 3rd percentile. Total score: 490, 31st percentile.

Do you have any questions or ideas what you would like to try?
I will be running a few more scenarios - feel free to suggest what other scenarios would be interesting to test. Thank you!

Important Clarification: we have a strong reason to believe that even though GMAT Prep is the closest algorithm to the GMAT, it is most likely not identical. Some of these scenarios may result into a different outcome when attempted on the real test. We so far have no reports to confirm or dismiss these results based on the test day experience.

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