Editing Mars effect (section)

===The Zelen test===
In 1975 [[Paul Kurtz]]'s journal ''The Humanist'' published an article on astrology criticizing Gauquelin, to which the latter and his wife Françoise responded. Then Professor [[Zelen's design|Marvin Zelen]], a statistician and associate of the recently founded Committee for the Scientific Investigation of Claims of the Paranormal (CSICOP, now known as the [[Committee for Skeptical Inquiry]] (CSI)), proposed in a 1976 article in the same periodical that, in order to eliminate any demographic anomaly, Gauquelin randomly pick 100 athletes from his data-set of 2,088 and check the birth/planet correlations of a sample of babies born at the same times and places in order to establish a [[control group]], giving the base-rate (chance) expectation for comparison (The 100 random athletes later expanded into a subsample of 303 athletes).

In April 1977 CSICOP researcher [[George O. Abell]] wrote to Kurtz stating that Zelen's test had come out in the Gauquelins' favour. The Gauquelins also performed the test that Professor Zelen had proposed and carried out and found that the chance Mars-in-key-sector expectation for the general population (i.e., non-champions) was about 17%, significantly less than the 22% observed for athletic champions. However the subsequent article by Zelen, Abell and Kurtz did not clearly state this outcome but rather questioned the original data. In a rebuttal of the Gauquelins' published conclusion, Marvin Zelen analysed the composition, not of the 17,000 non-champions of the control group, but of the 303 champions, splitting this secondary subsample (which was already nearly too small to test 22% vs 17%) by eliminating female athletes, a subgroup that gave the results most favourable to Gauquelin, and dividing the remaining athletes into city/rural sections and [[Paris]]ian/non-Parisian sections.

Before and after publication of Zelen's results astronomer and charter CSICOP member [[Dennis Rawlins]], the CSICOP Council's only astronomer at the time, repeatedly objected to the procedure and to CSICOP's subsequent reporting of it. Rawlins privately urged that the Gauquelins' results were valid and the “Zelen test” could only uphold this and that Zelen had diverted from the original purpose of the control test, which was to check the base rate of births with Mars in the "key" sectors. It appeared to him that the test had minimised the significance of the Mars/key-sector correlations with athletes by splitting the sample of athletes and that the experimenters, who were supposed to be upholding scientific standards, were actually distorting and manipulating evidence to conceal the result of an ill-considered test.

The Kurtz-Zelen-Abell analysis had split the sample primarily to examine the randomness of the 303 selected champions, the non-randomness of which Rawlins demonstrated in 1975 and 1977. Zelen's 1976 "Challenge to Gauquelin" had stated: "We now have an objective way for unambiguous corroboration or disconfirmation ... to settle this question", whereas this aim was now disputed. Rawlins made procedural objections, stating; "... we find an inverse correlation between size and deviation in the Mars-athletes subsamples (that is, the smaller the subsample, the larger the success) – which is what one would expect if bias had infected the blocking off of the sizes of the subsamples".<ref>The Zetetic ([[Skeptical Inquirer]]) 2, no. 1, Fall/Winter 1977, p.&nbsp;81</ref>

CSICOP also contended, after reviewing the results, that the Gauquelins had not chosen randomly. They had had difficulty finding sufficient same-week and same-village births to compare with champions born in rural areas and so had chosen only champions born in larger cities. The Gauquelins' original total list of about 2,088 champions had included 42 Parisians and their subsample of 303 athletes also included 42 Parisians. Further, Paris is divided into 20 ''[[Arrondissements of Paris|arrondissements]]'', different economic classes and ethnic groups typically inhabiting different arrondissements. The Gauquelins had compared the 42 Parisian champions (who had been born throughout Paris) to non-champions of only one arrondissement. If the 22% correlation was an artifact partly based on factors such as rural recordkeeping, economic, class or ethnic differences in birth patterns, this fact would be blurred by this non-random selection.