researchers showed that the square root of the number of adult fleas y has a quadratic relationship with the nest humidity index x. Specify the population regression model for this situation.

Exercise 28.7:

Nestling mass and nest humidity. Researchers investigated the relationship between nestling mass, measured in grams, and nest humidity index, measured as the ratio of total mass of water in the nest divided by nest dry mass, for two different groups of great titmice parents.2 One group was exposed to fleas during egg laying and the other was not. Exposed parents were coded as 1, and unexposed parents were coded as 0. Use the output above, obtained by fitting a multiple regression model with parallel lines for the two groups of parents, to answer the following questions.

(a) Identify the regression model for predicting nestling mass from nest humidity index for the two groups of great titmice parents.
(b) Based on your model, do you think that nestling mass was higher in nests of birds exposed to fleas during egg laying? Explain.
(c) What is the value of the regression standard error? Interpret this value.
(d) What is the value of the squared multiple correlation coefficient? Interpret this value.