A Random Sample of 15 Telephone Calls in an Office

Short Answer

A random sample of 15 telephone calls in an office showed the duration of each call and whether it was a local or a long distance call.
$\begin{array}{ccc}&\text { Duration }\\\text { Call Number } & \text { In Minution } &\text { Type of Call }\\1 & 2 & \text { local } \\2 & 12 & \text { long distance } \\3 & 10 & \text { local } \\4 & 3 & \text { local } \\5 & 5 & \text { long distance } \\6 & 6 & \text { local } \\7 & 3 & \text { local } \\8 & 5 & \text { local } \\9 & 8 & \text { local } \\10 & 4 & \text { local } \\11 & 5 & \text { local } \\12 & 4 & \text { local } \\13 & 5 & \text { local } \\14 & 4 & \text { local } \\15 & 9 & \text { long distance }\end{array}$
a. What is the point estimate for the average duration of all calls?
b. What is the point estimate for the standard deviation of the population?
c. What is the point estimate for the proportion of all calls that were long distance?