Assignment:
The snail dataset contains percentage water content of the tissues of snails grown under three different levels of relative humidity and two different temperatures.
(a) Use the command xtabs(water ~ temp + humid, snail)/4 to produce a table of mean water content for each combination of temperature and humidity. Can you use this table to predict the water content for a temperature of 25?C and a humidity of 60%? Explain.
(b) Fit a regression model with the water content as the response and the temperature and humidity as predictors. Use this model to predict the water content for a temperature of 25?C and a humidity of 60%?
(c) Use this model to predict water content for a temperature of 30?C and a humidity of 75%? Compare your prediction to the prediction from (a). Discuss the relative merits of these two predictions.
(d) The intercept in your model is 52.6%. Give two values of the predictors for which this represents the predicted response. Is your answer unique? Do you think this represents a reasonable prediction?
(e) For a temperature of 25?C, what value of humidity would give a predicted response of 80% water content.
Your answer must be typed, double-spaced, Times New Roman font (size 12), one-inch margins on all sides, APA format and also include references.