Two variables of interest are the dependent 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 = 1,388 births, bwght = 119.77 − 0.514 cigs
(i) what is the predicted birth weight when cigs = 0? what about when cigs = 20? comment on the difference.
(ii) does this simple regression necessarily capture a causal relationship between the child’s birth weight and the mother’s smoking habits? explain.
(iii) to predict a birth weight of 125 ounces, what would cigs have to be?