9An unbiased die with six sides is tossed three times What i

9.An unbiased die with six sides is tossed three times. What is the probability that you will get at least two sixs?

10.

The distribution of the number of hours that college students watch TV per week is unimodal with a mean of 3.7 and a standard deviation of 5. Is it appropriate to use the normal model to approximate the percentage of hours of TV watching within one standard deviation of the mean?

Select one:

a. Yes, it is appropriate to use the normal model because we expect 68% of the observations to be within one standard deviation of the mean.

b. We cannot decide unless we have the original data.

c. No, it is not appropriate to use the normal model because it is impossible to watch negative hours of TV per week.

d. We cannot decide whether or not to use the normal model unless we have the median.

Solution

Probability of six=1/6, probability of not six=5/6

Probability of ateleast two six=probability of two six+probability of three six=3C2(1/6)(1/6)(5/6)+3C3(1/6)(1/6)(1/6)=15/216+1/216=16/216=2/27