3.15. A regional opera company has tried three approaches to solicit donations from 24 potential sponsors. The 24 potential sponsors were randomly divided into three groups of eight, and one approach was used for each group. The dollar amounts of the resulting contributions are shown in the following table.

(a) Do the data indicate that there is a difference in results obtained from the three different approaches?
Use ( $ 0.05.

(b) Analyze the residuals from this experiment and comment on model adequacy.

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Approach 123 Contributions (in $) 1000 1500 1200 1800 1600 1100 1000 1250 2 1500 1800 2000 1200 2000 1700 1800 1900 3 900 1000 1200 1500 1200 1550 1000 1100