Question

In Exercises 9–20, use the data in the following table, which lists drive-thru order accuracy at popular fast food chains (data from a QSR Drive-Thru Study). Assume that orders are randomly selected from those included in the table.

	McDonald’s	Burger King	Wendy’s	Taco Bell
Order Accurate	329	264	249	145
OrderNotAccurate	33	54	31	13

Fast Food Drive-Thru Accuracy If one order is selected, find the probability of getting an order that is not accurate.

Short answer

The probability of getting an order that is not accurate is equal to 0.117.

Step-by-step solution

Given information

The given data depicts the number of food orders from four different outlets under two categories, accurate order and inaccurate order, in a tabulated form.

Define probability

The probability of an event E has the following expression:

$P\left(E\right)=\frac{\text{Number}\text{of}\text{favorable}\text{outcomes}}{\text{Total}\text{number}\text{of}\text{outcomes}}$

Compute the probability 

The following table shows all the subtotals and the grand total.

	McDonald’s	Burger King	Wendy’s	Taco Bell	Total
Order Accurate	329	264	249	145	987
Order Not Accurate	33	54	31	13	131
Total	362	318	280	158	1118

Let E be the event of getting an inaccurate food order.

The total number of inaccurate food orders is denoted by $O_C$. The value is computed below:

$$\begin{gathered} O_C=33+54+31+13 \\ =131 \end{gathered}$$

Let the total number of orders be denoted by N.

The probability of getting an inaccurate food order is calculated as shown below:

$$\begin{gathered} P\left(E\right)=\frac{O_C}{N} \\ =\frac{131}{1118} \\ =0.117174 \end{gathered}$$

Therefore, the probability of getting a food order that is not accurate is equal to 0.117.