a) Find the mean first = sum of scores/number of scores
Subtract each of the scores from the mean and square each difference. Find the sum of these squares. Divide that by the number of scores to get variance.
Standard deviation = square root of variance
b) Z = (score-mean)/SD
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability (.15) and its Z score.
Insert data in above equation to get the raw score.
c) Use same equation and table.
a) What is the standard deviation of the set of data?
b) What raw score will have 15% of the data set above it?
c) If I have a raw score of 21 what percentage of the scores, are below my score?
16, 16, 89, 76, 24, 45, 98, 20, 22, 28, 34, 35, 76, 67, 48, 37
2 answers
a) 27.08