Refer to the previous exercise.
a. What is the expected number of calls among the 25 that involve a fax message?
b. What is the standard deviation of the number among the 25 calls that involve a fax message?
c. What is the probability that the number of calls among the 25 that involve a fax transmission exceeds the expected number by more than 2 standard deviations?
In previous exercise
A particular telephone number is used to receive both voice calls and fax messages. Suppose that 25% of the incoming calls involve fax messages, and consider a sample of 25 incoming calls.