# Lunn and McNeil show a data set comparing two methods of surgical tattoo removal.19 In addition to

## Question:

a. Create a logistic regression model using Method, Gender, and Depth to estimate the probability that a tattoo was removed successfully. Based on Wald’s test, which variables appear to be significant? Based on the likelihood ratio test (H0: β1 = β2 = β3 = 0 versus Ha: at least one of the coefficients is not zero), can we conclude that at least one of these terms is significant?

b. Create a logistic regression model using only Gender and Depth to estimate the probability that a tattoo was removed successfully. Based on Wald’s test, which variables appear to be significant? Based on the likelihood ratio test (H0: β1 = β2 = 0 versus Ha: at least one of the coefficients is not zero), can we conclude that at least one of these terms is significant?

c. Use the drop-in-deviance test to compare the models in Parts A and B. Can you conclude that Method is related to the probability of success?

d. Construct a model using only Method to predict the probability of a successful removal. What do Wald’s test and likelihood ratio test reveal?

e. Explain why the drop-in-deviance test in Part C is better than the approach in Part D for determining if Method is related to the probability of a successful tattoo removal.

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**Related Book For**

## Practicing Statistics Guided Investigations For The Second Course

**ISBN:** 9780321586018

1st Edition

**Authors:** Shonda Kuiper, Jeff Sklar