Truncation Bias Research Articles

Fecundability and its relation to age in a sample of Taiwanese women

Abstract In this paper reliable estimates of mean fecundability at marriage for a sample of heterogeneous Taiwanese women are obtained by using a set of data collected retrospectively. The effects of 'truncation bias' and 'memory bias' are estimated by studying the relationships between mean fecundability and the duration of marriage. Then the variations in fecundabilities by age at marriage are studied. The data are taken from an intensive fertility survey of married women between the ages of 20 and 39 conducted in Taichung city of Taiwan towards the end of 1962 prior to a year-long family planning action programme. Fecundability, the probability of conception in the absence of contraception, is estimated by using a Type I geometric model and is estimated from the observed distribution of first pregnancy intervals-the period between the onset of marriage and the beginning of first conception. The estimated fecundability level relatively free from truncation and memory bias is 195±3 per 1.000 women. The fecundability level increases with wife's age at marriage (up to 25) independently of its association with the duration of marriage.

Socio-economic correlates of fecundability in a sample of taiwanese women

Abstract Estimates of fecundability (monthly probability of conception) in the absence of contraception are derived from the frequency distribution of conceptive delays immediately following marriage, reported by 2,443 married women aged 20 to 39 included in the Taichung (Taiwan) Intensive Fertility Survey of 1962. Average fecundability of women is positively associated with their socio-economic status. These differentials are not accounted for by differences among socio-economic groups with respect to memory and truncation biases (associated with the marriage duration), wife’s age at marriage, or unreported premarital conceptions. A Multiple Classification Analysis suggests that among the socio-economic characteristics, husband’s education, rural background, and modern family type are the more important predictors of fecundability. The importance of genetic factors as opposed to cultural factors in producing these socio-economic differences in fecundability can not be evaluated systematically. Moreover, the relation of a couple’s privacy, their attitude toward family building, and patterns of mate selection to their socioeconomic status would have to be taken into account before the differences in fecundability could be attributed to factors such as nutrition, health, or infections which might directly influence their physiological ability to conceive.