Question: The data set BWGHT.RAW contains data on births to women in the United States. Two variables of interest are the dependant variable, infant birth weight in ounces (bwght) and an explanatory variable, average number of cigarettes the mother smoked per day during pregnancy (cigs). The following simple regression was estimated using data on n = 1388 births: bwght hat = 119.77 - .514 cigs

a. What is the predicted birth weight when cigs = 0? What about when cigs = 20 (one pack per day)? Comment on the difference.

b. Does this simple regression necessarily capture a causal relationship between the child’s birth weight and the mother’s smoking habits? Explain.

c. To predict a birth weight of 125 ounces, what would cigs have to be? Comment.

d. What would the coefficients be if birth weight is measured in grams (hint: 1 ounce=28.35 gram).