A study of teenage suicide included a sample of 96 boys and 123 girls between the ages of 12 and 16 years selected scientifically from admissions records to a private psychiatric hospital Suicide attempts were reported by 18 of the boys and 60 of the girls. We assume that the girls constitute a simple random sample from a population of similar girls and likewise for the boys

a) Construct a 99% confidence interval for the difference between the proportions of suicide attempts of boys and girls. 

b) Is the above confidence interval valid? Why or why not? 

c) Is there a significant difference between the proportions of suicides attempts of boys and girls based on your confidences interval in part a) why or why not?