The data file Birthweight_Smoking, which contains data for a random sample of babies born in
Pennsylvania in 1989. This data is in the Blackboard assignment 2 section. The data include the
baby's birth weight together with various characteristics of the mother, including whether she
smoked during the pregnancy. For this question, you will investigate the relationship between
birth weight and smoking during pregnancy. (You can use R to solve this. Please attach your R
code under your answers as well if you indeed use R.)
2.1 In the sample: (6 points)
2.1.1 What is the average value of Birthweight for all mothers?
2.1.2 For mothers who smoke?
2.1.3 For mothers who do not smoke?
2.2 Use the data in the sample to estimate the difference in average birth weight for
smoking and nonsmoking mothers. (10 points)
2.2.1 What is the standard error for the estimated difference in 2.2?
2.2.2 Construct a 95% confidence interval for the difference in the average birth weight for
smoking and nonsmoking mothers.
2.3 Run a regression of Birthweight on the binary variable Smoker. (6 points)
2.3.1 Explain how the estimated slope and intercept are related to your answers in parts 2.1 and
2.2.
2.3.2 Explain how the SE() is related to your answer in 2.2.1.
2.3.3 Construct a 95% confidence interval for the effect of smoking on birth weight.
2.4 Do you think smoking is uncorrelated with other factors that cause low birth weight?
That is, do you think that the regression error term\textendash say, $u$\textendash has a conditional mean of 0
given Smoking ($X_i$)? Yes, or No? and Why? (3 point)