The random variable X is exponentially distributed, where X represents the time it takes for a person to choose a birthday gift. If X has an average value of 26 minutes, what is the probability that X is less than 30 minutes? (Do not round until the final step. Round your answer to 3 decimal places.)

Respuesta :

Answer:

0.685 = 68.5% probability that X is less than 30 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]

If X has an average value of 26 minutes

This means that [tex]m = 26, \mu = \frac{1}{26}[/tex]

What is the probability that X is less than 30 minutes?

[tex]P(X \leq 30) = 1 - e^{-\frac{30}{26}} = 0.685[/tex]

0.685 = 68.5% probability that X is less than 30 minutes