A sample of two groups , A and B having 100 people each who have a disease were taken to test efficacy of a medicine . The medicine is given to group A but not to group B ( which is called the control group ) ; otherwise , the two groups are treated identically . It is found that in groups A and B , 75 and 65 people , respectively , recover from the disease .

a ) At significance levels of 0.01 , test the hypothesis that the medicine helps to cure the disease .

b ) If each group consists of 300 people and if 225 people in group A and 195 people in group B are cured . At significance levels of 0.01 , test the hypothesis that the medicine helps to cure the disease .

c ) Is the result of part b different from that of part a Comment on the result