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1 Studies in the History of Statistics and Probability ... - Sheynin, Oscar

1 Studies in the History of Statistics and Probability ... - Sheynin, Oscar

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*several dozen. The totality µ ican thus be considered (if <strong>the</strong>Mendelian model is valid) a sample with <strong>the</strong>oretical distribution be<strong>in</strong>g<strong>the</strong> st<strong>and</strong>ard normal law.Kolmogorov studied two most numerous series <strong>of</strong> Ermolaeva’sexperiments <strong>and</strong> respectively two samples (2.6) with 98 <strong>and</strong> 123observations. [...] He obta<strong>in</strong>ed λ = 0.82 <strong>and</strong> 0.75. The probability <strong>of</strong> abetter fit (a lesser λ) was 0.49 <strong>and</strong> − 0.37 so that those values <strong>of</strong> λ werequite satisfactory.A purely statistical <strong>in</strong>vestigation thus changed <strong>the</strong> results: an allegedrefutation <strong>of</strong> <strong>the</strong> Mendelian laws became <strong>the</strong>ir essential confirmation.Apart from <strong>the</strong> opponents <strong>of</strong> <strong>the</strong> Mendel <strong>the</strong>ory Kolmogorov alsomentioned <strong>the</strong> work <strong>of</strong> his followers, En<strong>in</strong> (1939) <strong>in</strong> particular. He didnot subject that paper to a detailed analysis, but <strong>in</strong>dicated that <strong>the</strong>agreement with <strong>the</strong> ma<strong>in</strong> model <strong>of</strong> Bernoulli trials was too good (<strong>the</strong>frequencies concern<strong>in</strong>g separate families deviated from p = 1/4 lessthan it should have occurred accord<strong>in</strong>g to <strong>the</strong> ma<strong>in</strong> model <strong>of</strong> Bernoullitrials). A detailed analysis is <strong>in</strong>structive from many viewpo<strong>in</strong>ts <strong>and</strong> Iam <strong>the</strong>refore provid<strong>in</strong>g En<strong>in</strong>’s ma<strong>in</strong> results.He considers <strong>the</strong> segregation <strong>of</strong> <strong>the</strong> tomato hybrids accord<strong>in</strong>g todiffer<strong>in</strong>g leaves: normal <strong>and</strong> potato-like. His results are separated <strong>in</strong>totwo groups depend<strong>in</strong>g on <strong>the</strong> time <strong>of</strong> sow<strong>in</strong>g <strong>the</strong> seeds <strong>of</strong> <strong>the</strong> hybridplants <strong>in</strong> <strong>the</strong> hothouse (February or April). [...]All <strong>the</strong> material except one observation is shown on Fig. 3. Weought to decide now what k<strong>in</strong>d <strong>of</strong> statistical treatment is needed. Inapplied ma<strong>the</strong>matical statistics <strong>the</strong> application <strong>of</strong> each given statisticaltest is objective, [...] but which criteria should be chosen is anessentially subjective question. The answer depends on whichs<strong>in</strong>gularities <strong>of</strong> <strong>the</strong> data seem suspicious <strong>and</strong> <strong>the</strong> statistician more orless adequately converts this impression <strong>in</strong>to statistical tests. There areno common rules, we can only discuss examples.The matter is that <strong>in</strong> pr<strong>in</strong>ciple any given result <strong>of</strong> observations isunlikely (<strong>and</strong> <strong>in</strong> our present case <strong>of</strong> a cont<strong>in</strong>uous law <strong>of</strong> distribution<strong>the</strong> probability <strong>of</strong> any concrete result is simply equal to zero).Therefore, a criterion can also be found that will reject any hypo<strong>the</strong>sisconsidered <strong>in</strong> any circumstances. We ought not to be here superdiligent<strong>and</strong> only admit criteria hav<strong>in</strong>g a substantial sense suitable for<strong>the</strong> concrete natural scientific problem. On <strong>the</strong> o<strong>the</strong>r h<strong>and</strong>, if notwish<strong>in</strong>g to reject some tested hypo<strong>the</strong>sis, it will be usually possible tochoose such criteria that will not do that. Here, we are alreadyspeak<strong>in</strong>g about <strong>the</strong> honesty <strong>of</strong> <strong>the</strong> statistician.Concern<strong>in</strong>g <strong>the</strong> material presented on Fig. 3, we first turn ourattention to <strong>the</strong> empirical function for <strong>the</strong> first series <strong>of</strong> observations. Itis situated completely above <strong>the</strong> <strong>the</strong>oretical function <strong>and</strong> <strong>in</strong> general isquite well smoo<strong>the</strong>d by some straight l<strong>in</strong>e (dotted on <strong>the</strong> Figure)almost parallel to <strong>the</strong> <strong>the</strong>oretical. The entire difference is some shift to<strong>the</strong> left. S<strong>in</strong>ce we deal with a shift (we see it perfectly well, but do notknow whe<strong>the</strong>r it is significant or not), we ought to apply <strong>the</strong> test basedon <strong>the</strong> sample mean. It is equal to – 0.64 <strong>and</strong> its variance is1/ 11 ≈ 0.30; to rem<strong>in</strong>d, <strong>the</strong> tested hypo<strong>the</strong>sis concerns <strong>the</strong> st<strong>and</strong>ardnormal distribution for <strong>the</strong> values <strong>of</strong> µ*. The deviation exceeds two103

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