Birth weights of babies in Guatemala were found to have mean 2,860 grams and standard deviation 440 grams.
a. The distribution of birth weights would be somewhat left-skewed, but sample mean birth weight for samples of several hundred babies would be close to normal, according to what theorem?
b. The mean weight of 572 babies of mothers who cooked on open wood fires (as opposed to cleaner fuels like gas or electricity) was 2,820 grams. Find the z-score for this sample mean.
c. Characterize a sample mean weight of 2,820 for samples of size 572 taken from the population of Guatemalan birth weights as unusually low, a bit low, or quite typical.
d. If those 572 babies differed from the general population of babies only with respect to type of cooking fuel used by the mother, would the sample suggest that cooking with open wood fires while pregnant may lead to smaller babies?
e. What are some other variables whose values may differ for mothers who cook with various types of fuel, and which may also impact the babies' birth weights? (In other words, what are some possible confounding variables?)