Question 2 Part (a) Using the “Bus Maintenance.xls” file, carry out a t-test in Excel (with α = 0.05) that tests whether there is a difference in mean maintenance costs between buses with Diesel engines and those with gasoline engines. Note that the decision of which of the t-tests in Excel to use depends on your result from Question 1. You must submit your actual Excel file with the output as part of the assignment. Part (b) Based on the t-test, what is your decision (“reject” or “do not reject”) regarding the null hypothesis that the two population means are equal to each other? Indicate on which part of the Excel output you base your decision. Part (c) Explain what you answer to part (b) means at a level that can be understood by a high school senior.

(a) When you perform the t-test in excel you should get the following:
t=-0.2006236844p=.8416030944df=66.72581946bar(x_1)=448.7179487 bar(x_2)=451.7 SX1=71.8375172SX2=51.5592394n1=39n2=30
(b) Do not reject the null hypothesis as p>.05
(c) If the means of the two samples are really equal, p gives the probability that random samples from the two populations could look like the samples we obtained. Here the probability is quite high. If the probability was low enough (here less that 0.05) we would reject the null hypothesis and say that the populations probably have differing means.
http://mathworld.wolfram.com/Studentst-Distribution.html