A study classified each of 134 lawyers into one of four groups based on observation and an interview. The 62 lawyers in group A were categorized as having high levels of stimulation and support and average levels of public spirit. The 52 lawyers in group B had low stimulation, average support, and high public spirit. Group C contained 7 lawyers with average stimulation, low support, and low public spirit. The 13 lawyers in group D were assessed as low on all three criteria. Salary levels for these four groups were compared. The sample means were 7.87 for group A, 7.47 for group B, 5.14 for group C, and 3.69 for group D. The F ratio calculated from these data was 25.60.
a. Prepare the complete analysis of variance table.
b. Test the null hypothesis that the population mean salaries are the same for lawyers in these four groups.