2B. (a) An exponential distribution has probability density function S (x) = -e¯z/a, x 2 0. %3D Show that the mean of the distribution is a and the variance is a². (b) A machine contains two belt drives, of different lengths. These have times to failure which are exponentially distributed, with mean times a and 2a. The machine will stop if either belt fails, and the failures of the belts are independent. Show that the chance that the machine is still operating after a time a from the start is e 32.

A First Course in Probability (10th Edition)
10th Edition
ISBN:9780134753119
Author:Sheldon Ross
Publisher:Sheldon Ross
Chapter1: Combinatorial Analysis
Section: Chapter Questions
Problem 1.1P: a. How many different 7-place license plates are possible if the first 2 places are for letters and...
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Statistics and Probability
2B.
(a) An exponential distribution has probability density function
ƒ (x) =
x 2 0.
Show that the mean of the distribution is a and the variance is a².
(b) A machine contains two belt drives, of different lengths. These have times to failure which
are exponentially distributed, with mean times a and 2a. The machine will stop if either belt
fails, and the failures of the belts are independent. Show that the chance that the machine is
still operating after a time a from the start is e 32.
Transcribed Image Text:2B. (a) An exponential distribution has probability density function ƒ (x) = x 2 0. Show that the mean of the distribution is a and the variance is a². (b) A machine contains two belt drives, of different lengths. These have times to failure which are exponentially distributed, with mean times a and 2a. The machine will stop if either belt fails, and the failures of the belts are independent. Show that the chance that the machine is still operating after a time a from the start is e 32.
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