At a certain discount store, the number of people in checkout lines varies. The probability model for the number of people in a randomly chosen line is: $\begin{array} { l c c c c c c }
\text { Number in } & 0 & 1 & 2 & 3 & 4 & 5 \
\text { line } & & & & & & \
\text { Probability } & 0.08 & 0.15 & 0.20 & 0.22 & 0.15 & 0.20
\end{array}$
What is the mean number of people in a line?
A) 2.5
B) 15.92
C) 2.81
D) 2.89

Question

At a certain discount store, the number of people in checkout lines varies. The probability model for the number of people in a randomly chosen line is: $\begin{array} { l c c c c c c } 
\text { Number in } & 0 & 1 & 2 & 3 & 4 & 5 \
\text { line } & & & & & & \
\text { Probability } & 0.08 & 0.15 & 0.20 & 0.22 & 0.15 & 0.20
\end{array}$ 
What is the mean number of people in a line?
A) 2.5
B) 15.92
C) 2.81
D) 2.89

Quizplus · Accepted Answer

The mean or expected value of a probability distribution can be found by multiplying each possible value by its probability and adding them together. 
Thus, 
Expected value = (0)(0.08) + (1)(0.15) + (2)(0.20) + (3)(0.22) + (4)(0.15) + (5)(0.20) 
Expected value = 2.81
Therefore, the mean number of people in a line is 2.81.

At a Certain Discount Store, the Number of People in Checkout