probability and percentile problem

Oct 2019
27
1
united states
For each probability and percentile problem, draw the picture.

Suppose that the useful life of a particular car battery, measured in months, decays with parameter 0.025. We are interested in the life of the battery.

Give the distribution of X.
X ~

I believe that is exponential distribution x ~Exp(1/0.025) but one question said Find the probability that a car battery lasts more than 38 months. (Round your answer to four decimal places.) I tried P(x equal or more 38) and use the formula e to the power of -mc an get zero. could someone tell me what I am doing wrong?
 

Walagaster

MHF Helper
Apr 2018
219
143
Tempe, AZ
For each probability and percentile problem, draw the picture.

Suppose that the useful life of a particular car battery, measured in months, decays with parameter 0.025. We are interested in the life of the battery.

Give the distribution of X.
X ~

I believe that is exponential distribution x ~Exp(1/0.025) but one question said Find the probability that a car battery lasts more than 38 months. (Round your answer to four decimal places.) I tried P(x equal or more 38) and use the formula e to the power of -mc an get zero. could someone tell me what I am doing wrong?
You haven't told us what form your exponential distribution formula uses. If its pdf is $\lambda e^{-\lambda x}$ you get the integral $\int_{38}^{\infty}.025 e^{-.025 x} dx= .3867$, which seems reasonable since the mean is $\mu = \frac 1 \lambda = 40$.
 
Last edited:
Oct 2019
27
1
united states
Thank you so much that helped.