Forced expiratory volume (FEV) is a measure of the rate of airflow (L/min) during one deep exhalation. For each of 75 students, FEV was measured three times, and those results were averaged to give a summary FEV number. Some of the students were varsity soccer players. The table below shows mean summary values broken down by group.25

For these data, SS(Sex) = 544,398; SS(Soccer) = 136,610; SS(interaction) = 1,207; and SS(within) = 662,408.
(a) Prepare an interaction graph (like Figure 11.7.3) to investigate whether the male versus female difference is the same for soccer players as for non soccer players.
(b) Does the interaction graph from part (a) suggest that there is an interaction present? If so, what does that mean? If not, what does that mean?
(c) Carry out an F test for interactions; use α = 0.10.
(d) Given the result of the test in part (c), is it appropriate to test the null hypothesis that there is no soccer versus non soccer difference in mean FEV? If so, then conduct that test using α = 0.10. If not, then explain why not.

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Female, Female, Male, Male soccer soccer soccer soccer no 396 14 no yes 472 560 653 24 yes Mean 17 20