Proportional confidence interval?

[stein74]

1. An important issue facing Americans is the large number of medical malpractice lawsuits and the expenses that they generate. In a study of 1228 randomly selected medical malpractice lawsuits, it is found that 856 of them were later dropped or dismissed (based on data from the Physician Insurers Associations of America).

a. Based on this sample what proportion of medical malpractice lawsuits were dropped or dismissed?




b. Is the sample size large enough to construct a confidence interval?





c. List any assumptions made.





d. Compute a 99% confidence interval estimate of the proportion of medical malpractice law suits that were dropped or dismissed.






e. Does it appear that the majority of such suits are dropped or dismissed? Explain.



stuck on this problem, can some please explain how to do it