Example 2 described an experiment in which telephone callers to an airline were put on hold with an advertisement, Muzak, or classical music in the background. Each caller who was chosen was also randomly assigned to a category of a second factor: Whether the message played was five minutes long or ten minutes long. (In each case, it was repeated at the end.) The table shows the data classified by both factors and the results of a two-way ANOVA.

a. State the null hypothesis to which the F test statistic in the Message row refers.
b. Show how to use mean squares to construct the F test statistic for the Message main effect, report its P-value, and interpret.
c. On what assumptions is this analysis based?

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Telephone holding times by type of recorded message and repeat time Repeat Time Message Advertisement Muzak Classical Ten Minutes 8, 11, 2 1,4, 3 13, 8, 15 Five Minutes 5.1 0, 6 7.9 Source Message Repeat Error Total DF MS 2 149.20 74.60 7.09 0.011 23.51 23.51 2.24 0.163 11 115. 69 10.52 14 288.40