Consider a binomial experiment with n = 8 trials where the probability of success on a single trial is p = 0.15. (For each answer, enter a number. Round your answers to three decimal places.) (a) Find P(r = 0). Incorrect: Your answer is incorrect. (b) Find P(r ≥ 1) by using the complement rule.

We are given his four test scores out of the five tests he will receive, so all we need to do is solve for the last test score. We can do this by setting up an equation where (85 + 81 + 75 + 67 + x)/5 = 80. In this equation, x represents Sam's last test score that he will have to make in order to achieve an 80 percent average in his class. Now all we have left to do is solve for x.

(85 + 81 + 75 + 67 + x)/5 = 80
(308 + x)5 = 80
308 + x = 400
x = 92

Final Sam must achieve 92 percent on his next test to achieve an average of exactly 80 percent.