“Storks Deliver Babies (p = 0.008)”, 2001-06 (; backlinks):
This article shows that a highly statistically-significant correlation exists between stork populations and human birth rates across Europe.
While storks may not deliver babies, unthinking interpretation of correlation and p-values can certainly deliver unreliable conclusions.
[Keywords: teaching, correlation, statistical-significance, p-values]
…Testing The Stork-Birth Relationship: The white stork (Ciconia ciconia) is a surprisingly common bird in many parts of Europe, and data on the number of breeding pairs are available for 17 European countries (1999, personal communication); the latest figures, covering the period 1980–10199034ya, are given in Table 1, along with demographic data taken from Britannica Yearbook for 1990.
Plotting the number of stork pairs against the number of births in each of the 17 countries, one can discern signs of a possible correlation between the two (see Figure 1).
The existence of this correlation is confirmed by performing a linear regression of the annual number of births in each country (the Final column in Table 1) against the number of breeding pairs of white storks (column 3). This leads to a correlation coefficient of r = 0.62, whose statistical-significance can be gauged using the standard t-test, where t = r · √[(n − 2)/(1 − r2)] and n is the sample size. In our case, n = 17 so that t = 3.06, which for …n − 2 = 15 degrees of freedom, which leads to a p-value of 0.008.
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