PROBLEM SET 1

Show your work for problems 1 - 5

A shopping mall estimates the probability distribution of the number of stores mall customers

actually enter, as shown in the table.

x 0 1 2 3 4 5 6

p(x) .04 .19 .22 .28 .12 .09 .06

1. Find the mean number of stores entered

2. Find the standard deviation of the number of stores entered

3. What is the probability that a randomly selected customer will enter fewer than 4 stores?

4. A certain brand of flood lamps has a lifetime that is normally distributed with a mean

of 3,750 hours and a standard deviation of 300 hours. What proportion of these lamps will last

for more than 4,000 hours?