The speed with which consumers decide to purchase a product was investigated in the Journal of Consumer Research (August 2011). The researchers theorized that consumers with last names that begin with letters later in the alphabet will tend to acquire items faster than those whose last names begin with letters earlier in the alphabet-called the last name effect. MBA students were offered free tickets to an event for which there was a limited supply of tickets. The first letter of the last name of those who responded to an email offer in time to receive the tickets was noted as well as the response time (measured in minutes). The researchers compared the response times for two groups of MBA students: (1) those with last names beginning with one of the first nine letters of the alphabet and (2) those with last names beginning with one of the last nine letters of the alphabet. Summary statistics for the two groups are provided in the table.

a. Construct a 95% confidence interval for the difference between the true mean response times for MBA students in the two groups.
b. Based on the interval, part a, which group has the shorter mean response time? Does this result support the researchers' last name effect theory? Explain.

First 9 Letters: A- Last 9 Letters: R-Z Sample size: Mean response time (minutes): Standard deviation (minutes): 25 19.38 7.12 25 25.08 10.41