The service life of an incandescent light bulbs used domestically was
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
Years light bulb was used before failure (x) 0 1 2 3
Probability of x years 0.1 0.3 0.5 0.1
This is a simple problem showing how to calculate variance and mean value (average) in a probability problem.