1. A measure of the chance of an event occurring.

Usage Notes

  1. Quantitatively, likelihood is typically expressed as either:
  2. Qualitatively, likelihood is typically expressed using an Ordinal Scale (high, medium, low).
Be careful when using ordinal scales to express likelihood. It is impossible to use an ordinal scale with mathematical operations because “High x Low” does not yield a comparative result.

Historical Notes

  1. In English, “likelihood” has been distinguished as being related to but weaker than “probability” since its earliest uses. The comparison of hypotheses by evaluating likelihoods has been used for centuries, for example by John Milton in Aeropagitica: “when greatest likelihoods are brought that such things are truly and really in those persons to whom they are ascribed”.