A seven year medical research study reported that women whose mothers took the drug DES during pregnancy were twice as likely to develop tissued abnormalities that might lead to cancer as were women whose mothers did not take the drug.

a. For the population of women showed 63 developed tissue abnormalities that might lead to cancer. Provide a descriptive statistic that could be used to estimate the number of women out of 1000 in this population who have tissued abnormalities and for the population of women whose mothers did not take the drug DES during pregnancy , what is the estimate of the number of women out of 1000 who would be expected to have tissue abnormalities?

b. Medical studies often use a relatively large sample. Why?