fun with statistics

I’m sure I’m going to get this wrong, but here’s what I want to do: I want to see what my percentile would be if I was comparing myself to the GRE taking folks (so I can compare my math test with my score in the GRE practice test last weekend). I’m going to assume that my math class’ normal distribution is shifted by 20 percentage points to the left in relation to the distribution for the math section of the GRE. This would because my class is not representative of folks headed to grad school. You’d expect that the population at large (i.e. those not headed to grad school) would, on average, score worse than folks headed to grad school. Also, I’ll just assume that the distribution curves look similar (equal stdev).

Anyway, the average on my recent test (see previous post) was 45% and the standard deviation was 20%. Given the above, I’ll assume that students headed to grad school would have averaged 65% and because I don’t know what I’m doing, I’ll assume that the standard deviation is exactly the same. NOTE: it may not be fair to assume that the deviation would be similar in the two samples as my class may consist of some students that are going to grad school (high scorers as a group) and the rest aren’t (low scorers as a group). Intuitively, I feel like this would increase the spread in the scores. But anyway…

I scored 2.6 standard deviations above average which is the 99th percentile. Where would this put me on the ‘headed to grad school’ distribution curve? About the 95th percentile…

Look, I have to make myself feel better. I’m taking another practice GRE this weekend. We’ll see how I do.


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