CAT Exams percentile drop off, second half

[CABBA]

I'm just wondering if anyone has an opinion regarding the issue that I had on my last 2 CAT exams. The issue is that I am having a difficult time holding my percentile rank on the second half of the exam (i.e. i'm seeing patches of wrong answers particularly on the second half). I've come to the forums looking for ideas because on my first 3 CAT's I've found that my %-ile rank tends to nose dive around the second half of the test and i'm not sure why.
I expected this to occur on CAT1, since it was my first attempt, and running low on time i was forced to guess in order to finish all the questions on time. However on the last 2 CATs that I took, I unexpectedly saw that around the half way point my score fell off badly even though I was holding a decent pace. For example on CAT 3, which I took yesterday my quantitative percentile rank was at 65% on question 17 and i was 1:30 below the target time. From there my score ended up at the 47%-ile.
Similarly on the verbal section of the CAT I took yesterday, I was at an 85%'ile rank going into question 22, 1:30 behind schedule and then proceeded to drop to a 51%'ile by the time I finished the test.
This exact thing happened to me on CAT 2. I was close to being on time, but around the half way point of both Q and V, i saw a heavy drop off of my score. Maybe i was incredibly lucky at the beginning and fell to my actual level, or maybe i hit a mental wall. It just seems strange to me. Maybe I shouldn't be looking at the %'ile rank any way.. I'm not sure.
My final combined score for CAT3 was a disappointing 550. I recently completed the InterAct course and am targeting a score in the low to mid 600's and would like to know if anyone has any experience with what factors I might look into, that might allow me to better hold my score towards the second half of the test. When I look at the score report, i see stretches where i get several questions wrong, but i still receive 700-800 level questions. This makes me wonder if maybe i'm just drawing some bad luck. I have considered that fatigue may be an issue but i feel mentally strong when going through the CAT's under full testing conditions.
I'm planning to try a GMAT Prep practice exam in the next couple of days to compare, but any feedback is welcome.

[CABBA]

After doing numerous practice sets from the OG guides, and attempting to increase my stamina using some of the suggestions that i've come across on the forums, I did my first GMAT Prep exam today. I scored a 660 (47Q/34V). I lost my timing some what on the Verbal section and i notice that this caused several wrong answers in the second half. Timing is going to be critical for me going forward because it seems as though a small time deficiency (and the natural response of trying to speed up) has a significant impact on my accuracy. All this being said my goal seems more attainable now, i just wanted to add some input after doing the GMAT Prep Exam.

[StaceyKoprince]

(FYI for future: each post is listed in the queue according to the date of the LAST post in the chain - so when you posted the second time, it pushed your post later in the queue. I just want to make sure you know that so that you can hold off, if you want, next time - so that you don't have to wait so long for a response.)

You're looking at the right things and asking the right questions. There are several possibilities - you'll need to dig a little more to determine the cause(s).

It's entirely possible that you are hitting a mental wall - mental fatigue is a very real factor on this test. Try some of those second-half problems again. How many of the ones you missed can you do when you're fresh (and, of course, still within normal timing)? How many provoke the reaction, "Wait, how did I miss that?? I know how to do that!!" We all make careless mistakes occasionally, but if that is happening more than 1-2 times for half a section, then there's a mental fatigue or sloppiness factor going on.

It could also be that you did get a bit lucky in terms of distribution of strengths and weaknesses - so check for that. Did you happen to get more weaknesses in the second half? What are those weaknesses? If you have too many holes in your foundation, your score will be pulled down. On the GMAT, it's much better to be a "generalist": pretty good across most topics. Specialists (really good at some, really bad at others) have a tougher time getting a good score.

Finally, another thing could have happened. Your score was good and your timing was good halfway. Did you then start messing up the timing? Sometimes, this is what happens: people work their way to their top level and then (of course!) are given even harder problems. They spend too much time on some or all of those but get them wrong anyway (since the problems are too hard) AND they blow a bunch of mental energy, so when they get other questions that they do know how to do, they miss those...and it's all downhill from there.

Take a look at the data and the problems to see whether any of those is contributing to the problem - and let us know what you find.

Re: feeling mentally strong, the bizarre thing about mental fatigue is that you often don't know you're experiencing it. (Because the thing that could tell--your brain--is fatigued!) Take a look at this:
https://www.manhattanprep.com/gmat/blog ... you-crazy/

The article is on a related / adjacent topic, but it discusses common symptoms of mental fatigue. Do any ring a bell?