Some varieties of nematodes, roundworms that live in the soil and feed on the roots of lawn grasses and other plants, can be treated by the application of nematicides. Data collected on the percent kill of nematodes for various rates of application (dosages given in pounds per acre of active ingredient) are as follows:

MINITAB diagnostic plots for Exercise 12.64

Use an appropriate computer printout to answer these questions:
a. Calculate the coefficient of correlation r between rates of application x and percent kill y.
b. Calculate the coefficient of determination r2 and interpret.
c. Fit a least-squares line to the data.
d. Suppose you wish to estimate the mean percent kill for an application of 4 pounds of the nematicide per acre. What do the diagnostic plots tell you about the validity of the regression assumptions? Which assumptions may have been violated? Can you explain why?

Transcribed Image Text:

Rate of Application, x 23 Percent Kill, y 50, 56, 48 63, 69, 71| 86, 82, 76 94, 99, 97 Normal Probability Plot of the Residuals (response is y) -10 10 Residual Residuals versus the Fitted Values (response is y) 5.0 2.5 0.0 2.5 5.0 50 60 70 80 90 100 Fitted Value