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.

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.

The probability of an event E has the following expression:

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

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

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.