A study was conducted to measure the effect of a fungicide treatment on the survival rate of botrytis blight. Botrytis blight samples were divided into 20 groups, each consisting of about 100 samples and exposed to different levels of chemicals in a fungicide. The output of a logistic regression model is below, where concS represents the concentration of a sulfur in the fungicide and concCu represents the concentration of a copper in the fungicide. Required:
a. What is the probability of survival for a botrytis blight sample exposed to a sulfur concentration of 0.7 and a copper concentration of 0.9?
b. Suppose you wanted to test if the coefficient for concCu is equal to -0.2. What z-value would you use for this test?
c. Construct an approximate 95% confidence interval for the coefficient of concCu.