It has been estimated that between 1945 and 1971, as many as 2 million children were born to mothers treated with diethylstilbestrol (des), a nonsteroidal estrogen recommended for pregnancy maintenance. the fda banned this drug in 1971 because research indicated a link with the incidence of cervical cancer. the article "effects of prenatal exposure to diethylstilbestrol (des) on hemispheric laterality and spatial ability in human males" (hormones behav., 1992: 62–75) discussed a study in which 10 males exposed to des and their unexposed brothers underwent various tests. this is the summary data on the results of a spatial ability test: x ¼ 12: 6 (exposed), y ¼ 13: 7, and standard error of mean difference ¼ .5. test at level .05 to see whether exposure is associated with reduced spatial ability by obtaining the p-value.