A major department store chain is interested in estimating the average amount its credit card customers spent on their first visit to the chain's new store in the mall. Fifteen credit card accounts were randomly sampled and analyzed with the following results: x = $50.50 and s2 = 400. A 95% confidence interval for the average amount the credit card customers spent on their first visit to the chain's new store in the mall is:

Question

a. $50.50 ± $11.00
b. $50.50 ± $9.09
c. $50.50 ± $11.79
d. $50.50 ± $10.12
e. $50.50 ± $11.08

Answer 1

95% = mean ± 1.96SEm

SEm = s/√n

s = √(s^2)

I'll let you do the calculations.

Answer 2

10.12

Answer 3

$50.50+-11.08$