A clinical trial tests a method designed to increase the probability of conceiving a girl. In the study 400 babies were born, and 340 of them were of them were girls. Use the sample data to construct

A clinical trial tests a method designed to increase the probability of conceiving a girl. In the study 400 babies were born, and 340 of them were of them were girls. Use the sample data to construct 99% confidence interval estimate of the percentage of girls were born. Based on the result, does the method appear to be effective?