A second file on DocDepot named Marks.mtp contains the final exam percentages of students in ADM2304A in the Fall 2011 semester. Assume that the class can be considered a random sample from the population of commerce students.

The Attend variable is coded as follows:
Attend = 0 if the student came to class less than 70% of the time
Attend = 1 if the student came to class more than 70% of the time

(a) Examine the distributions of the sample data to determine if the 2 sample t-test is valid.

(b) Assuming unequal population variances, test whether there is a difference in average final exam marks between the two groups in the population. Use the critical value approach and the .01 level of significance. Perform the test manually after using Minitab to summarize the data and/or to calculate the degrees of freedom.

(c) Now manually find or calculate the p-value for your sample result.

(d) Finally calculate manually the 99% confidence interval for the true difference between the two population means.

(e) Explain how the results in (c) and (d) are consistent with your conclusion in (b).

(f) If the 2-sample t-test were not valid, then identify another test you could use. Explain.