1. A company has reviewed their sales figures and finds that an average of 3 of their bestselling televisions are returned each month because they are not working properly and according to the warranty must be replaced.
a. What is the probability that in a single month none of these televisions are returned?
b. What is the probability that in a single month 3 or 4 of these televisions are returned?
c. What is the probability that in two months only one of these televisions is returned?
d. What is the average number of returns per month?
e. What is the standard deviation of monthly returns?
f. What is the probability that the time between the next two returns will be 3 days or less?
g. What is the average time between returns in a month?
h. What is the standard deviation of the time between returns?
2. Women's heights are normally distributed with a mean of 162 cm and standard deviation of 16 cm.
a. What percentage of heights are greater than 180 cm?
b. What height is at the 90th percentile ?
c. What height is at the 40th percentile?
d. In a sample of 5, what is the probability that the average height is less than 180 cm?