A Researcher Would Like to Determine Whether a New Tax

Essay

A researcher would like to determine whether a new tax on cigarettes has had any effect on people's behavior.During the year before the tax was imposed,stores located in rest areas on the state thruway reported selling an average of µ = 410 packs per day with σ = 60.The distribution of daily sales was approximately normal.For a sample of n = 9 days following the new tax,the researcher found an average of M = 386 packs per day for the same stores.
a. Is the sample mean sufficient to conclude that there was a significant change in cigarette purchases after the new tax. Use a two-tailed test with α = .05.
b. If the population standard deviation was σ = 30, is the result sufficient to conclude that there is a significant difference?
c. Explain why the two tests lead to different outcomes.