ABSTRACT
The distribution of intervals between successive births in a particular serial position is approximately log normal. There are three factors of interest: family size, birth order and sequence of sex. Since the distribution of intervals between births is approximately log normal, the authors calculate the average of log, although in the present circumstances taking logarithms is something of a refinement; throughout natural logs are used. Also the different observations across each line can be used to provide some indication of variability. The variation involved is natural variation. The full data would consist at one level of a set of frequency distributions, one distribution for each combination of sequence number and sex pairing. In more detail one would have for each family a set of intervals and sexes. All that can be done with the available data is to describe as concisely as possible any systematic structure.
