statistics
posted by emily .
do you want to own your won candy store? start up costs (units in 1,000) for a random sample of candy stores are: (95, 173, 129, 95, 75, 94, 116, 100, 85)
Use an 80% confidence interval to test the null hypothesis that the mean start up cost is 118. Justify answer.

80% = mean ± 1.28 SEm
SEm = SD/√n
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
I'll let you do the calculations.