One of the saddest world statistics is the HIV/AIDS rate in African countries. For example, the HIV/AIDS rate in Sierra Leone among people aged 15 to 45 is reported to be 7%. If doctors were to randomly screen 250 residents of Sierra Leone in this age group, what is the

a. Expected number of people in the group who have HIV/AIDS? Explain the meaning of this
expected value.

b. Variance of the random variable “number of people in the group who have HIV/AIDS”?

c. Standard deviation of the random variable “number of people in the group who have HIV/AIDS”?