A researcher would like to determine if a new tax on cigarettes has had any effect on people’s behavior. Before the tax, stores located in rest areas on the state thruway reported selling an average of µ = 415 packs per day with ? = 50. The distribution of daily sales was approximately normal.
For a sample of n = 16 days following the new tax, the researcher found an average of M = 386 packs per day for the same stores.
Is the new mean number of packs per day significantly different from the number of packs per day sold before the tax?
a. What is the value of test statistic that you calculate?
(2 point)
b. What is the critical value of Z with a two tailed test at .05?
- point)
c. Is the sample mean sufficient to conclude that there was a significant change in cigarette
purchases after the new tax, using a two-tailed test with ? = .05? Say why yes or why no.
(2 point)
d. If the population standard deviation was ? = 75, is the result sufficient to conclude that
there is a significant difference? Show how the calculations are different here.
- point)
e. Explainwhythe two tests lead to different outcomes. Explain what this says about the SD and hypothesis testing.
(2 point)
