Question

It is hypothesized that the average number of Girl Scout cookie boxes sold per day at a local mall is 200. To test
this, 25 days were randomly examined during days Girl Scout cookies were being sold. The resulting sample
mean and standard deviation were 180 and 40, respectively. Provide a test at the 0.05 level of significance.
Assume a normal distribution.

Answer 1

Given

n = 25

= 180

= 200

s = 40

Here

Null hypothesis , H₀ :   = 200

Alternate hypothesis , H_a :     200

Test statistic

t = -2.5

Here

D.F = n-1 = 25-1 = 24

P-value = 0.019654 ~ 0.0196 (Two -tailed test)

Here

P-value is less than

Reject null hypothesis. There is sufficient evidence to suggest that the average number of Girl Scout cookie boxes sold per day at a local mall is 200.