If I scored 333 on an exam, and the mean is 250 with a standard deviation of 50, how did I do? Am I in the 80th percentile or something, or lower? Thanks
2007-09-10 10:43:59 · 3 answers · asked by heyhey022001 2 in Science & Mathematics ➔ Mathematics
To calculate how you did you transform to a Normal distribution with mean=0 and SD=1
If X~N(250, 50) and Y~N(0, 1)
The P(X<=332) = P(Y<=(332-250)/50) = P(Y<=1.64)
You then look this value up in a normal table (or use PROBSDIST function in Excel)
P(Y<=1.64)=0.9494
i.e. P(scoring 332 or less) = 0.9494 (say round to 0.95)
P(scoring 333 or above)=0.05
The score is within the top 5%.
Now if only this were your exam grade instead of a homework question...!
2007-09-10 10:53:43 · answer #1 · answered by piscesgirl 3 · 1⤊ 0⤋
I took an IQ test 4 weeks ago. I scored 143. I don't know how good that is though.
2016-05-21 08:03:47 · answer #2 · answered by ? 3 · 0⤊ 0⤋
95th percentile!
Well done!
Normal with mean = 250 and standard deviation = 50
x....................P( X <= x )
333.0000.......0.9515
2007-09-10 10:48:05 · answer #3 · answered by gebobs 6 · 0⤊ 1⤋