1. On the Time Required for Conception.
- Author
-
Sheps, Mindel C.
- Subjects
DATE of conception ,POPULATION statistics ,HUMAN fertility ,DISTRIBUTION (Probability theory) ,STATISTICAL correlation ,STATISTICS - Abstract
Assuming that the monthly chance of conceiving, fecundability, is constant for any one woman during the period of observation, but varies from one woman to another in an unspecified way, this paper investigates the expected incidence of first conceptions and the distribution of conception delays. The expected monthly incidence of first conceptions is a decreasing function of time. The mean, variance and higher moments of the distribution of fecundability (p) may be estimated from incomplete data referring to only the first few months of exposure. The distribution of conception delays is distinguished from the distribution of the number of trials needed for conception, and the moments of each are derived. When appropriate data are available to calculate the moments of the conception delay or the number of trials, the squared and cubed deviations of i/p about the harmonic mean fecundability can be estimated. These statistics may be useful descriptions of the discrepancy between an observed distribution and theoretical values expected in a homogeneous population. The correlation between two successive conception delays is also discussed in the article.
- Published
- 1964
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