Mean or Expected Value and Standard Deviation · Exercise 27

Suppose that the PDF for the number of years it takes to earn a bachelor of science (B.S.) degree is given as in.

$$\begin{array}{cc}\text{x}& \text{P(x)}\\ \text{3}& \text{.05}\\ \text{4}& \text{.40}\\ \text{5}& \text{.30}\\ \text{6}& \text{.15}\\ \text{7}& \text{.10}\end{array}$$
On average, how many years do you expect it to take for an individual to earn a B.S.?

OpenStax, Statistics · §4.2 Mean or Expected Value and Standard Deviation · Exercise 27