There was a typo in #7 of Homework #9. The question should read:
"Calculate estimates of the RERI, its 95% confidence interval for additive interaction between the SNP and age (continuous) on lung cancer, adjusted for sex, smoking, and college graduate. Show you Stata commands and calculations and explain your findings. (To calculate RERI with a continuous variable, we must specify two levels we want to compare. In this example, compare age 75 to age 55 years.)"
An updated version of the Homework #9 file has also been posted to the course website.