Refer to Exercise 11.40. Often in drug evaluations, a logarithmic transformation of the dose levels will yield a linear relationship between the response variable and the ­independent variable. Let xi be the natural logarithm of the dose levels, and evaluate the regression of the ­response of the drug in the 15 test tubes to the transformed independent variable: yi = β0 + β1xi + É›i.
a. Plot the response of the drug versus the natural logarithm of the dose levels. Does it appear that a linear model is appropriate?
b. Fit a linear regression model to these data.
c. From a plot of the residuals, do these appear to be a possible lack of fit of the linear model?
d. Conduct a test for lack of fit of the lineat regression model.
In exercise

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Dose level Response 73 101 15,17 20,21,19 23,29 28,31,30 16 32 64