🎯  Host a contest 📢  Promote a contest 📝  Submit a contest

Expected Value

Expected value is a way of averaging possible outcomes by how likely each one is. You multiply the value of each outcome by its probability and add the results. A prize worth €500 with a 1-in-1,000 chance contributes €0.50, which is the expected value of that entry before you subtract anything you spent. The number is not a prediction of what you will receive; it is a fair-price benchmark for a gamble you are thinking about taking.

The calculation in one line

Value times probability, summed across outcomes. If a promotion awards ten €100 prizes and one €1,000 prize among 5,000 eligible entries, the total prize money is €2,000, so the average entry returns €0.40. Notice that this works even when you cannot pin down your own single chance, as long as you know the total prizes and the number of competing entries.

Then subtract what the entry costs you

Entry "cost" is usually time and personal data rather than money. Twenty minutes of work to build a submission against a €0.40 expected return is a bad trade unless you enjoyed the twenty minutes. If a promotion requires travel, a purchase, or a paid subscription to take part, include that too. Also remember that headline prize figures can be gross of other deductions, including tax; in many places prize value is reportable, so ask a qualified professional before treating a large number as spendable.

For a random drawing, the honest probability needs the eligible entry count, and organizers almost never publish it. Any expected value you compute is therefore built on a guess. Rather than pretending to precision, run two scenarios: a plausible field size and a much larger one. If the conclusion changes between them, the number was never doing any work.

Expected value ignores what the prize means to you

Two prizes with the same face value can matter very differently. A hotel stay you can actually use is worth more to you than cash of equal size that goes to a bill, and neither is worth the same as something you would never buy. Expected value treats money as interchangeable; your life does not.

You will not get the average

An average only appears if you repeat the same gamble thousands of times. You will enter a handful of promotions, and almost all of them will return nothing. That is not a reason to skip them; it is a reason to size entries so that the likely outcome, no prize, is perfectly acceptable, and to keep the cost of playing small.

A practical way to use it

Ask one question before you enter: if I knew the realistic odds, would the effort still feel worth it? Cheap entries in promotions you like pass easily. Anything expensive in time, money, or data deserves a harder look, and a large advertised prize is not automatically a good trade.

Common misconception

That a positive expected value means the entry is worth taking. With unknown entry counts and conditions you cannot verify, the sign of the number is usually decoration. A huge headline prize can produce an expected value that looks attractive while the probability stays negligible and the payout remains subject to rules you have not read.

Key takeaways

  • Expected value equals value times probability, added across outcomes; it is a benchmark, not a forecast.
  • Subtract real costs: time, required purchases, data, and possible tax consequences of a win.
  • The probability input is usually a guess, so test your answer against a bigger field.
  • Averages describe many repetitions; individual entries almost always return nothing.
  • Let the effort-versus-value question decide, and reserve caution for expensive entries.