Archive for birthrate

latest issue of Significance

Posted in Statistics with tags , , , , on March 20, 2017 by xi'an

The latest issue of Significance is bursting with exciting articles and it is a shame I do not receive it any longer (not that I stopped subscribing to the RSS or the ASA, but it simply does not get delivered to my address!). For instance, a tribune by Tom Nicolls (from whom I borrowed this issue for the weekend!) on his recent assessment of false positive in brain imaging [I covered in a blog entry a few months ago] when checking the cluster inference and the returned p-values. And the British equivalent of Gelman et al. book cover on the seasonality of births in England and Wales, albeit witout a processing of the raw data and without mention being made of the Gelmanesque analysis: the only major gap in the frequency is around Christmas and New Year, while there is a big jump around September (also there in the New York data).

birdfeedA neat graph on the visits to four feeders by five species of birds. A strange figure in Perils of Perception that [which?!] French people believe 31% of the population is Muslim and that they are lacking behind many other countries in terms of statistical literacy. And a rather shallow call to Popper to running decision-making in business statistics.

More babies on Valentine’s Day and less babies on Halloween?!

Posted in Kids, Statistics, Travel with tags , , , , , on February 14, 2012 by xi'an

(Source: Levy et al., 2011)

In the weekend edition of Le Monde, more precisely in the Sciences section, I read a report on a 2011 study made by Levy et al. who observed that the birthrate drops at Halloween and surges at Valentine’s Day… The above graph illustrates the fact for Halloween, with a significant [meaning?!] 5.3% decrease for spontaneous births. The increase for Valentine’s Day is 3.6% (still for spontaneous births). Even though those data are the result of a survey of all births in the United States over 11 years, thus unlikely to exhibit sampling biases,  I am fairly bemused both by the phenomenon and by the interpretation made in the study, namely that “pregnant women may be able to control the timing of spontaneous births” (while I find less astounding that “scheduled births are also influenced by the cultural representations of the two holidays“, even though there may be an administrative bias as well). Being unfamiliar with the U.S. procedure for delivery of birth certificates (and how much both Valentine’s Day and Halloween are of a public holiday), I wonder if this may be a reporting rather than biological bias…

Reading now into the paper (thanX, A.!), I see that “these holidays have the advantage of widespread participation, but without ordinarily resulting in the absence of physicians from work, as on certain federal holidays“, so my first idea that the Halloween gap [more pronounced than the Valentine surge] could be due to reduced medical or administrative staff does not seem so likely. The authors mention using an analysis of covariance model to build their significance test, adjusting for weekday and year effect, even though neither the model [what are the covariates?] nor the statistical analysis is provided in the paper. Looking at the equivalent of the above graph for Valentine shows more variability along the window of 15 days used by the authors. It would be fairly interesting to check throughout the years if other variations of that magnitude occur (and if they are always related to culturally significant days), before accepting the conclusion that “pregnant women can expedite or delay spontaneous births, within a limited time frame, in response to cultural representations“…