Feral pigs are controlled in Australia by lacing bait with sodium monofluoroacetate (SM). Anecdotal evidence suggests the pigs become bait shy to SM. An experiment was conducted to examine the validity of that evidence. Feral pigs were captured and fed pure wheat for a period. Diets were then changed and the difference in bait intake was observed. Four pigs each were fed a new diet of wheat only (Wht), wheat and water (WhtH20), wheat and water and dye (WhtH20Dye), wheat and water and SM (WhtH20SM), or wheat and water and dye and SM (WhtH20DyeSM). Half the pigs were females and half were males. The data is shown below. A negative intake change means the pig ate less after the diet change.

a) Assuming the standard deviations of intake change for each level of each factor separately meet the books criterion, complete a two-way analysis of variance of intake change including both factors at once. Interpret the results in terms of each factor and the interaction between the factors (P-values for the three tests).

b) Construct and report an interaction plot for the data with Sex as the trace variable.

c) Referring to the two-way ANOVA and the interaction plot, does the experiment support or refute the anecdotal evidence? Explain.

d) Construct a residual quantile-comparison plot for the model fit in part a). Does the plot give you confidence in, or raise suspicion over, the tests of part a)?

Sex F F F F F F F F F Bait IntakeChange Wht -0.261 Wht -0.035 WhtH20 -0.502 WhtH20 -0.329 WhtH20Dye -0.245 WhtH20Dye -0.086 WhtH2OSM -0.869 WhtH2OSM -0.644 WhtH20Dyes -0.832 WhtH2ODyes -1.205 Wht 0.183 Wht -0.043 WhtH20 -0.113 WhtH20 0.055 WhtH20Dye -0.044 WhtH20Dye 0.053 WhtH2OSM -1.246 WhtH2OSM -0.817 WhtH20Dyes -0.795 WhtH2ODyes -0.591 M M M M | M M EEEEEEEEEE M M M M M