Probability and Statistics

Question

In a study of statistics professors' salaries (USA) the following data was obtained:

n=16, x¯=$80000, s=$13000

Determine the 95% confidence interval for standard deviation (σ) of the population.

You may assume the population is normally distributed.

Answer 1

CI = x bar +/- zs/sqrn

CI = 80,000 +/- .1.96(13,000)/sqr16

or use z=2 with the empirical rule

= 80000 +/- about 2(3250)

= 80000 +/- 6500

= (73500, 86500)