Evaluating Your Practice Tests, Part 1 of 2

by , Sep 23, 2009

Practice tests are an invaluable component of any test-taker's study plan, but the most valuable thing is actually not the act of taking the practice test. Just taking a test doesn't help us to improve all that much. While taking a test, we are concentrating on doing (using everything we've learned up to that point); as a result, we're not really learning much.

The most valuable thing is actually the data that you can extract when you're done with the test; that's how you learn to get better and know what to study before you take another practice test. There are two main components to that data:

1. Statistics and metrics based on timing, difficulty level, percentage correct, question category, and so on
2. A thorough, analytical review of the specific questions that you saw on the test

This week, I'll take you through how I review the statistic and metrics from my own students' practice tests. I'll base my discussion on the metrics that are given in ManhattanGMAT tests, but you can extrapolate to other tests that give you similar performance data (note: you need per-question timing and difficulty level in addition to percentage correct/incorrect data). Next week, we'll take a look at how to review specific questions.

First, naturally, I look at the score. I also check whether the student did the essays (if she didn't, I assume the score is a little inflated); I also ask the student to tell me whether she used the pause button, took extra time, or did anything else that wouldn't be allowed under official testing guidelines.

Next, I look at the problem lists for the quant and verbal sections; the problem lists show each question, in order as it was given to the student, as well as various data about those questions. First, I scan down the "correct / incorrect" column to see whether the student had any strings of 4 or more answers wrong. If so, I also look at the time spent; perhaps the student was running out of time and had to rush. I also look at the difficulty levels because sometimes I'll see this: the difficulty level is high for the first problem or two, and the timing is also way too long. On the later questions, the difficulty level is lower, but the timing is also too fast. Essentially, the person had a sense that she spent too long on a couple of hard questions, so she sped up... and then she not only got the hard questions wrong but she also got the easier questions wrong because she was rushing.

I also look at the timing for the last five to ten problems in the section to see whether the person was rushing or had a lot of time left (meaning she rushed earlier in the section).

Next, I count the number of questions that fall into the "way too slow" category. Too much time is: 3+ minutes on quant or CR, and 2+ minutes on SC. RC is a bit trickier, because the timing for the first question includes the time spent to read the passage. If it's a first question, "too long" is above 5 minutes. If it's not a first question, "too long" is above 2.5 minutes. If there are more than a few, then the student has a timing problem. My next question: how significant is the problem?

For these "too slow" questions, I count how many there are, how much time was spent total, and how many were correct vs. incorrect. For quant, I also count how many were Problem Solving vs. Data Sufficiency. Finally, I see whether there are any patterns in terms of the content area (for example, perhaps three of the "too long" quant problems were geometry problems or two of the "too long" SC problems were modifier problems).

Next, I count how many "way too fast" incorrect questions there are. "Way too fast" is anything done in less than half the time it was supposed to be done (for example, "way too fast" would be less than 1 minute for a quant question). I do not, however, count incorrect "too fast" questions that are rated 700+ unless that student is scoring 700+; I assume the student (wisely) realized the problem was too hard, made a guess, and moved on. That's the only good reason to get something wrong in a "too fast" timeframe. Otherwise, these lower-level, too fast, incorrect questions represent missed opportunities - careless mistakes - and they were caused by the "too slow" questions from above.

All of the above is to quantify for the student just how bad the timing problem is. Literally just seeing the data can help students start to get over that mental hurdle ("I can get this right if I just spend some more time!") and start balancing their time better. And the stats on question type and content area will help the student to be more aware of where she tends to get sucked in.

Next, I run the assessment reports and look at the Assessment Summary. This tells me percentages correct for the five main question types, as well as average timing and difficulty levels. Problem areas are indicated by:

• Percentages correct below approximately 50%, especially when coupled with lower average difficulty levels (though I'm not worried if I see, say, 48% correct with an average difficulty level of 730 - that's a good result)
• Average timing that is 30 seconds (or more) higher or lower than it should be on average
• A big discrepancy (more than 20-30 seconds) in average time for correct vs. incorrect answers of the same type

I then go through the other reports (showing all of the problems divided into various sub-categories) while categorizing things into five buckets (though I may have to adjust my assessment if there are only one or two questions in a category):

1. 50% + correct plus timing within the expected timeframe (otherwise known as strengths)
2. Less than 50% correct plus timing in the expected timeframe (possible weaknesses in content area, methodology, etc, BUT check the difficulty levels; maybe this category just happened to be really hard on this test!)
3. Less than 50% correct plus timing way too fast (an average more than 30 seconds faster than it should be); are these really weaknesses or was the student just going too fast (and, naturally, making more careless mistakes)? Why was the student going too fast on these?
4. 50%+ correct plus timing way too slow (an average more than 30 seconds slower than it should be); these are still weaknesses even though the percentage correct is high! Figure out why the timing is higher and how you can do these more efficiently.
5. Less than 50% correct plus timing way too slow (an average more than 30 seconds slower than it should be); these are the biggest weaknesses, obviously. Get them wrong faster. Seriously - you're getting them wrong anyway, so start by just taking less time to get them wrong! That will improve your performance on all those ones on which you're currently rushing and making careless mistakes!

Click here to see the second article in this series, where we'll talk about how to review the specific questions, topics, and content areas that were tested on the exam.

Read other articles in this series:

• Evaluating Your Practice Tests, Part 1 of 2
• Evaluating Your Practice Tests, Part 2 of 2