Theory
The expected value is, in the long run, the same as the mean,. It is calculated in this way:
Example 1
You throw a die. What is the expected value of the number you roll?
Make a table with the possible outcomes and their probabilities:
1 | 2 | 3 | 4 | 5 | 6 | |
Example 2
You insure your laptop with an insurance company. The policy of the insurance company is to only compensate you under two circumstances:
Your laptop is stolen.
Your laptop is broken.
In the first case you’ll be compensated , while in the second case you’ll be compensated .
Assume the probability of your laptop being stolen is , and the probability of your laptop breaking is . To keep it simple, let’s assume that these probabilities are the same any given year.
and
The expected compensation during any given year then becomes