next up previous
Next: Random partitions Up: On the Paper of Previous: Some Examples

The significance levels in the research by Witztum, Rips and Rosenberg

Witztum, Rips and Rosenberg claim to have found an arrow sent by the author of the Book of Genesis, crossing thousands of years in its flight. But this arrow was not sent by the author of the Book of Genesis. The arrow was stuck by Witztum, Rips and Rosenberg themselves and they left their fingerprints.

In their 1987 preprint [3] which presented the situation after the second test was carried out, Witztum, Rips and Rosenberg write in the introduction as follows:

"For the string G however, for the unperturbed sample we obtained c(w,w') tending to zero with a probability against a null hypothesis of a uniform distribution that we estimate as $1.3 \cdot 10^{-9}$ for the first experiment and $1.2 \cdot 10^{-9}$ for the second (which gives the probability $1.8 \cdot 10^{-17}$ for the union of the samples)."

These numbers refer to the principal measure of significance used by WRR at that time for the two tests they made. The measure of significance used was later called the P2-statistics or the P2-score. In the Analysis Section of the same preprint the next digit is revealed so the numbers are $1.15 \cdot 10^{-9}$ and $1.29 \cdot 10^{-9}$, respectively.

The ratio between these two numbers is 1.1217. We will see that in view of the instability of the P2-statistics this ratio is extremely small. It is significantly small compared to random partitions of the 66 Rabbis into sets of 34 and 32 Rabbis respectively, it is significantly small compared to random perturbations of the original division of Rabbis, it is even substantially smaller than the typical effect of adding and deleting a single appellation to a single Rabbi.

The only explanation we can offer for this phenomenon is that there was an optimization process in the second experiment which stopped when the significance level of the first experiment was reached. Moreover, consider an optimization process in the second test which terminates with the addition of an appellation which brings the significance level beyond that of the first test. We can expect that the ratio of the significance levels of the two tests will be in the neighborhood of the square root of the effect of the last appellation. Indeed, the square root of the typical effect of adding an appellation is comparable to the ratio we witness.

It is worth noting that the astronomical significance levels cited above (from the 87 preprint [3]) are false due to wrong independence assumptions. A realistic way to measure the significance level suggested by Diaconis gives (for the second experiment) the value $1.6 \cdot 10^{-3}$.(See Section 7.)


next up previous
Next: Random partitions Up: On the Paper of Previous: Some Examples
Gil Kalai
9/2/1997