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

Solution :

This is the two tailed test .

The null and alternative hypothesis is ,

H₀ :   = 200

H_a :    200

= 180

= 200

s = 40

n = 25

df = 25 - 1 = 24

Test statistic =t

= ( - ) / s / n

= (180 - 200) / 40 / 25

= -2.5

Test statistic = -2.5

P-value = 0.0197

= 0.05

P-value <

Reject the 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 .