A field experiment was conducted to assess the effect of organic enrichment on the mean density of mosquito larvae. (Journal of the American Mosquito Control Association, June 1995.) Larval specimens were collected from a pond 3 days after the pond was flooded with canal water. A second sample of specimens was collected 3 weeks after flooding and enriching the pond with rabbit pellets. All specimens were returned to the laboratory and the number y of mosquito larvae counted in each specimen.

a. Write a model that will allow you to compare the mean number of mosquito larvae found in the enriched pond to the corresponding mean for the natural pond.

b. Interpret the β coefficients in the model, part a.

c. Set up the null and alternative hypotheses for testing whether the mean larval density for the enriched pond exceeds the mean for the natural pond.

d. The p-value associated with the global F test for the model, part a, was determined to be .004. Interpret this result.