# Example of calculation of the mean value and variance

The service life of an incandescent light bulbs used domestically was

investigated.

It was found that a light bulb can last up to 3 years, and the probability

distribution of the number of years a light bulb was used before failure is given

below:

Years light bulb was used before failure (x) 0 1 2 3

Probability of x years 0.1 0.3 0.5 0.1

(i) What is the mean service life of a light bulb?

(ii) What is the variance and standard deviation of a service life of a light

bulb?

https://brainmass.com/statistics/probability/example-calculation-mean-value-variance-343149

#### Solution Summary

This is a simple problem showing how to calculate variance and mean value (average) in a probability problem.

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