Question

An exponential random variable has a standard deviation of 16. Calculate The probability that it takes on a value < 11. Use 3 decimal places.

Answer 1

Answer:

$P(X$

And using the cdf we got:

$P(X$

Step-by-step explanation:

Previous concepts

The exponential distribution is "the probability distribution of the time between events in a Poisson process (a process in which events occur continuously and independently at a constant average rate). It is a particular case of the gamma distribution". The probability density function is given by:

$P(X=x)=\lambda e^{-\lambda x}, x>0$

And 0 for other case. Let X the random variable that represent the random variable of interest and we know that the distribution is given by:

$X \sim Exp(\lambda)$

We know the variance on this case given by :

$Var(X) = \frac{1}{\lambda^2}$

So then the deviation is given by:

$Sd(X) = \frac{1}{\sqrt{\lambda}}$

And if we solve for $\lambda$ we got:

$\lambda = (\frac{1}{16})^2 = \frac{1}{256}$

The cumulative distribution function for the exponential distribution is given by:

$F(x) = 1- e^{-\lambda x}$

Solution to the problem

And for this case we want to find this probability:

$P(X$

And using the cdf we got:

$P(X$