The length of time for one individual to be served at a cafeteria is an exponential random variable with mean of 6 minutes. Assume a person has waited for at least 4 minutes to be served. What is the probability that the person will need to wait at least 9 minutes total

43.46% probability that the person will need to wait at least 9 minutes total

Step-by-step explanation:

To solve this question, we need to understand conditional probability and the exponential distribution.

Conditional probability:

We use the conditional probability formula to solve this question. It is

In which

P(B|A) is the probability of event B happening, given that A happened.

is the probability of both A and B happening.

P(A) is the probability of A happening.

Expontial distribution:

The exponential probability distribution, with mean m, is described by the following equation:

In which is the decay parameter.

The probability that x is lower or equal to a is given by:

Which has the following solution:

The probability of finding a value higher than x is:

In this question:

Event A: Waited at least 4 minutes.

Event B: Waiting at least 9 minutes.

The length of time for one individual to be served at a cafeteria is an exponential random variable with mean of 6 minutes.

This means that

Probability of waiting at least 4 minutes.

Intersection:

The intersection between a waiting time of at least 4 minutes and a waiting time of at list 9 minutes is a waiting time of 9 minutes. So

What is the probability that the person will need to wait at least 9 minutes total

43.46% probability that the person will need to wait at least 9 minutes total

17 1/3

step-by-step explanation: