A large clinical trial of the effect of diet on breast cancer assigned women at random to either a normal diet or a low-fat diet. To check that the random assignment did produce comparable groups, we can compare the two groups at the start of the study. When asked if there is a family history of breast cancer: 3396 of the 19,541 women in the low-fat group and 4929 of the 29,294 women in the control group said "Yes". If the random assignemnt worked well, there should not be a significant difference in the proportions with a family history of breast cancer.
a) How significant is the observed difference? Carry out an appropriate test to help answer this question and show all of your work.
b) Describe a Type I and Type II error in this setting. Which is more serious? Please explain your answer.