17. A researcher is interested in understanding whether the mean time to complete a four-year college degree varies based on gender. She draws a sample of 12 college graduates-6 men and 6 women, and asks them how many years they took to finish their degree. Assuming that the data are drawn from a normal distribution, test the null hypothesis of no difference in mean years to degree competition between men and women. Men Women 18. A sociologist is interested in the effects of racism on birth weight. He constructs a dataset contain- ing the birth weight of African American children (in pounds) and their mothers' self-reported experience with racism during their pregnancy. He divides the children into two groups-those whose mothers reported experiencing no race-related incidents and those whose mothers reported at least one experience of racism during their pregnancy. Assuming birth rates to be normally dis- tributed, test the null hypothesis of no difference in mean birth weight between the two groups. No Exposure Exposure to Racism 7.2 8.4 7.6