noun
expectation
The average of a random variable’s possible values, weighted by their probabilities.
The expectation of a fair six-sided die roll is 3.5.
Etymology
Mathematics formalizes an anticipated result by weighting possible values according to their probabilities. The resulting expectation is a calculated average, not necessarily a value any single trial must produce.
More examples
- If a fair coin pays $2 for heads and nothing for tails, the expectation is $1.
- We calculate the expectation by weighting each possible value by its probability.
- These distributions have equal expectations but different spreads.
Forms
expectation · expectations
Similar words
- expected value
- An equivalent term explicitly naming the probability-weighted average.
- mean
- Also describes an average calculated from observed data.