14.15 Tom Frederick is the computer support manager for a large company whose employees have been complaining about “spam,” which many of us know as unwanted e-mail to solicit our money or our attention. Tom asked a sample of 9 employees to keep track of the number of spam messages they received during the previous week.

He then installed a spam “filter” into the e-mail system to block some of the spam by identifying key words that often appear in such messages. During the week following installation of the filter, the number of spam messages received by each of the 9 employees was again counted, with the results shown here. At the 0.05 level of significance, can we conclude that Tom’s filtering system is effective in reducing the weekly number of spam messages an employee receives?

Employee: Spam Messages, Before Filter Spam Messages, After Filter 1 2 3 4 5 6 7 8 9 28 27 24 18 23 28 25 20 28 19 25 25 19 20 21 18 21 22