About 1/4 of all adults in the United States have type O+ blood. If three randomly selected adults donate blood, find the probability of each of the following events. (Round your answers to four decimal places.) (a) All three are type O+. 0.0156 Correct: Your answer is correct. (b) None of them is type O+. 0.4219 Correct: Your answer is correct. (c) Two out of the three are type O+.

Arandom sample of 15 observations is used to estimate the population mean. the sample mean and the standard deviation are calculated as 172 and 63, respectively. assume that the population is normally distributed. a. with 99 confidence, what is the margin of error for the estimation of the population mean? b. construct the 99% confidence interval for the population mean. c. construct the 95% confidence interval for the population mean. d. construct the 83% confidence interval for the population mean. hint: you need to use excel function =t.inv.2t to find the value of t for the interval calculation.