The time between arrivals of customers at the drive-up window of a bank follows an exponential probability distribution with a mean of 10 minutes.
A. What is the probability that the arrival time between customers will be 7 minutes or less?
B. What is the probability that the arrival time between customers will be between 3 and 7 minutes?

Respuesta :

Answer:

a) 50.34% probability that the arrival time between customers will be 7 minutes or less.

b) 24.42% probability that the arrival time between customers will be between 3 and 7 minutes

Step-by-step explanation:

Exponential distribution:

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

[tex]f(x) = \mu e^{-\mu x}[/tex]

In which [tex]\mu = \frac{1}{m}[/tex] is the decay parameter.

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

[tex]P(X \leq x) = \int\limits^a_0 {f(x)} \, dx[/tex]

Which has the following solution:

[tex]P(X \leq x) = 1 - e^{-\mu x}[/tex]

The probability of finding a value higher than x is:

[tex]P(X > x) = 1 - P(X \leq x) = 1 - (1 - e^{-\mu x}) = e^{-\mu x}[/tex]

Mean of 10 minutes:

This means that [tex]m = 10, \mu = \frac{1}{10} = 0.1[/tex]

A. What is the probability that the arrival time between customers will be 7 minutes or less?

[tex]P(X \leq x) = 1 - e^{-\mu x}[/tex]

[tex]P(X \leq 7) = 1 - e^{-0.1*7} = 0.5034[/tex]

50.34% probability that the arrival time between customers will be 7 minutes or less.

B. What is the probability that the arrival time between customers will be between 3 and 7 minutes?

[tex]P(3 \leq X \leq 7) = P(X \leq 7) - P(X \leq 3)[/tex]

[tex]P(X \leq x) = 1 - e^{-\mu x}[/tex]

[tex]P(X \leq 7) = 1 - e^{-0.1*7} = 0.5034[/tex]

[tex]P(X \leq 3) = 1 - e^{-0.1*3} = 0.2592[/tex]

[tex]P(3 \leq X \leq 7) = P(X \leq 7) - P(X \leq 3) = 0.5034 - 0.2592 = 0.2442[/tex]

24.42% probability that the arrival time between customers will be between 3 and 7 minutes