Suppose that 69% of all adults over 55 wear glasses for reading. In a random sample of 70 adults over 55, what is the mean and standard deviation of those that wear glasses for reading? O mean: 48.3: standard deviation: 3.87 O mean: 21.7: standard deviation: 6.95 O mean: 21.7; standard deviation: 3.87 O mean: 48.3: standard deviation: 6.95 The number of students arrives during an office hour has a Poisson distribution. Furthermore, the experience shows that an average of three students arrives during an office hour. Find the probability that no students will arrive during an office hour. O 0.1225 O 0.0498 O 0.1108 0.0743
