statistics
posted by jo .
given the following population data, x=17,13,23,15,19,19,21,28 calculate the z score value for a score of 18.

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
Z = (scoremean)/SD
I'll let you do the calculations.