A doctor wants to determine if a new medication for cholesterol is more effective than the previous medication. The doctor informs his patients of the new medication and asks if they want to participate in a study. Patients who are currently taking medication for cholesterol are randomly selected and given the new medication. After two months, the patients’ cholesterol levels are checked.

Assume that there is a 11% rate of disk drive failure in a year. a. if all your computer data is stored on a hard disk drive with a copy stored on a second hard disk drive, what is the probability that during a year, you can avoid catastrophe with at least one working drive? b. if copies of all your computer data are stored on four independent hard disk drives, what is the probability that during a year, you can avoid catastrophe with at least one working drive?