Observations on the relationship between frequency and timing of intercourse and the probability of conception.

Abstract Several aspects of stochastic models as they relate to the monthly probability of conception are explored. In particular a method of obtaining the required probability distributions proceeding from a rather general description of human behaviour is presented. The number of acts of intercourse per month is considered as a random variable rather than being taken as a fixed constant. The pattern of intercourse is characterized mathematically. The construction of the probability function is presented and illustrated numerically. he Weibull distribution is shown to illustrate considerable flexibility in describing these differing patterns of intercourse quantitatively. The resulting probabilities of conception vary considerably under changing parameter values even when the expected number of acts of intercourse is taken to be nearly equal. The relevance of these considerations is discussed.