STAT 5303 Assignment 10

Chemical Control of Fire Ants

A study was conducted to determine the effectiveness of 4 chemicals developed to control fire ants. It was suspected that the type of environmental conditions in which the chemicals are placed might impact their effectiveness. For this reason the researchers randomly selected 5 locations from a large selection of locations; each one representing a randomly selected environment. To reduce the effect of different colonies of ants and the type of mounds they inhabit, the researchers created 40 artificial mounds and populated each with 50,000 ants having similar ancestry. Two mounds were assigned to each of the 20 chemical-location treatment combinations. The number of fire ants killed (in thousands) over a one-week period was then recorded. A description of the variables appearing in the dataset along with abbreviated names is as follows.

1. Chemical: Type of chemical applied on the mound (1,2,3,4).
2. Location: Environmental location of the mound (1,2,3,4,5).
3. Ants: Number of fire ants killed (in thousands).

Using these data, fit an appropriate linear model to predict number of ants killed, and summarize your findings. Specifically, carry out/answer the following questions:

• Write down an appropriate linear statistical model for this study, and indentify all the terms in your model.
• Fit the ANOVA model identifed above, treating chemicals as a fixed factor. Interpret and summarize your findings concerning all the terms being tested in the ANOVA table. If there are variance components give estimates for them.
• Assess the fit of your fitted model.
• Use Tukey's method to determine all pairwise differences among the chemical means. Which chemical(s) are the most effective at killing ants?

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Instructions:

• Typeset your results in the same format as Assignment 7.

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