An experiment was performed to measure the effects of two factors on the ability of cleaning solutions to remove oil from a piece of cloth. The factors were the concentration of soap (in percent by weight) and the percentage of lauric acid in the solution.

The experiment was repeated twice for each combination of factors. The outcome measured was the percentage of oil removed. The results are as follows.

a. Can you reject the hypothesis of no interactions? Explain.

b. Can the main effect of soap concentration on the amount of oil removed be interpreted? If so, interpret the main effect, using the α = 0.05 level of significance. If not, explain why not.

c. Can the main effect of lauric acid on the amount of oil removed be interpreted? If so, interpret the main effect, using the α = 0.05 level of significance. If not, explain why not.

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10% acid 25% acid 15% soap 52.3 54.5 57.4 53.7 25% soap 56.4 58.4 42.7 45.1