91影视

The table contains data concerning drivers of passenger cars involved in a head-on collision.

The idea of conditional probability is to compute an event鈥檚 probability relative to a prior event. It is computed as follows:

$P\left(A\left|B\right.\right)=\frac{P\left(A\text{and}B\right)}{P\left(B\right)}$

The addition rule is used to compute the probability of occurrence of event A or B stated as follows:

$P\left(A\text{or}B\right)=P\left(A\right)+P\left(B\right)-P\left(A\text{and}B\right)$

Tabulate the sum of rows and columns as follows:

Define the events as follows:

E: The randomly selected driver used a seatbelt.

F: The randomly selected driver was killed.

The number of drivers who used seatbelts is 10660.

The number of drivers killed is 8057.

The number of drivers who were killed and used seatbelts is 3655.

The total number of drivers surveyed is 18102.

The probabilities are computed as:

$$\begin{gathered} P\left(E\right)=\frac{10660}{18102} \\ P\left(F\right)=\frac{8057}{18102} \\ P\left(E\text{and}F\right)=\frac{3655}{18102} \end{gathered}$$

The probability that a randomly selected driver was killed or used or seatbelts is:

$$\begin{gathered} P\left(E\text{or}F\right)=P\left(E\right)+P\left(F\right)-P\left(E\text{and}F\right) \\ =\frac{10660}{18102}+\frac{8057}{18102}-\frac{3655}{18102} \\ =0.832 \end{gathered}$$

Thus, the probability that a randomly selected driver was killed or used seatbelts is 0.832.