Expected Value Formula and Calculation Steps
Expected value, also known as the mean, expectation, or first moment, refers to the long-term average of a random variable. Calculating EV involves finding the outcome you’d see on average if you repeated a process infinite times. Due to the law of large numbers, the average value of the variable approaches its EV as the number of repetitions reaches infinity.
In business, calculating EV can be more complex. Instead of straightforward probability—like rolling dice, for example—when every outcome has the same likelihood, business planning scenarios are influenced by factors that make some more likely than others.
Accounting for this reality means being thorough during the calculation process. Still, the process itself is straightforward. To calculate EV:
1. List each possible result and its likelihood to occur.
2. Multiply each result by its chance of happening.
3. Add them together to find the expected average over many repeats.
4. Confirm the probabilities across all outcomes sum to 1.
This approach works for any scenario where you can reasonably assign probabilities to different outcomes, from predicting sales ranges to guessing how many units will sell in a day to predicting hiring turnover. Even though you never “roll” exactly that average in a single try, a calculated EV figure tells you what to plan for over time.
Formula for Expected Value
The formula for expected value is:
EV = ∑ P(Xi) x Xi
where:
- X is a random variable
- Xi are specific values of X
- P(Xi) is the probability of Xi occurring
- EV of X equals each value of the random variable multiplied by its probability, and each of those products is summed.