Yates's contingency correction: When testing for independence in a contingency table, a continuous probability distribution, namely the chi-squared distribution, is used as an approximation to the discrete probability of observed frequencies, namely the multinomial distribution. To improve this approximation, Yates suggested a correction that involves subtracting 0.5 from the positive discrepancies (observed―expected) and adding 0.5 to the negative discrepancies before these values are squared in the calculation of the usual chi-squared test. If the sample size is larger, then the correction will have little effect on the value of the test statistic. Now no longer needed since exact tests can be used. [Everitt, B. S., 1992, The Analysis of Contingency Tables, 2nd edn, Chapman and Hall/CRC, Boca Raton, FL.]

Yea-saying: Synonym for acquiescence bias.

Years of potential life lost: A measure of the total number of life years lost due to premature death in a population from a certain cause. Premature death is usually defined as death earlier than some given value, for example, 65 or 75 years, or less than the appropriate average life expectancy. An indicator of premature mortality that gives more importance to the causes of death that occurred at younger ages than those that occurred at older ages. [British Medical Journal, 1990, 301, 429–32.]