The predicted relationship (and a 95% confidence
interval) between the daily number of births and the
daily number of sunspots resulting from a bivariate
regression together with a scatter plot of the two variables
is shown in Fig. 3. In contrast to the lack of an association
with the lunar cycle, there is a statistically significant
positive association between the two variables.
In order to explore the association between the number
of births and the lunar and solar cycle when controlling for
other potential confounding factors for the number of
births, Table 1 shows the results from multivariate
regression models for our full sample of births between
1920 and 1989 (column (1)) as well as the subsample of
births occurring between 1920 and 1949, 1950 and 1969,