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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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Such imag<strong>in</strong><strong>in</strong>g is a peculiar feature <strong>of</strong> ma<strong>the</strong>matical statistics, <strong>and</strong><strong>the</strong>re are no clear rules for empirically verify<strong>in</strong>g <strong>the</strong> results <strong>of</strong> <strong>the</strong>trials.3.4. Convergence <strong>in</strong> probability. For experimentally check<strong>in</strong>g it 5 along series <strong>of</strong> secondary trials is required <strong>and</strong> many samples <strong>of</strong> size nare needed. The author calls form<strong>in</strong>g many samples <strong>the</strong> pattern <strong>of</strong> many series,<strong>and</strong> <strong>the</strong> patterns <strong>of</strong> an extended <strong>and</strong> a fixed series are now both called <strong>the</strong> pattern <strong>of</strong>one (extended or fixed) series. In ma<strong>the</strong>matical statistics, an ensemble <strong>of</strong>sequences <strong>of</strong> trials is only imag<strong>in</strong>ed.3.5. Two compet<strong>in</strong>g ma<strong>the</strong>matical models <strong>of</strong> statistical stability.Thus, <strong>the</strong> traditional formulation <strong>of</strong> <strong>the</strong> limit <strong>the</strong>orems lack clear rulesfor verify<strong>in</strong>g ei<strong>the</strong>r <strong>the</strong> conditions, or conclusions. This is <strong>the</strong> reasonthat had formerly engendered an illusion, not completely dissociatedfrom, that <strong>the</strong> laws <strong>of</strong> large numbers <strong>the</strong>oretically deduce stability <strong>of</strong>means from homogeneity <strong>of</strong> trials. In particular, it followed thatma<strong>the</strong>matical statistics identifies statistical stability with convergence<strong>in</strong> probability as studied <strong>in</strong> <strong>the</strong> laws <strong>of</strong> large numbers. The Misesmodel <strong>of</strong> stability P = lim ω, n → ∞, is not usually mentioned. Theauthor quotes Kolmogorov’s pert<strong>in</strong>ent remark (1956, p. 262):Such considerations can be repeated an unrestricted number <strong>of</strong>times, but it is quite underst<strong>and</strong>able that it will not completely free usfrom <strong>the</strong> necessity <strong>of</strong> turn<strong>in</strong>g dur<strong>in</strong>g <strong>the</strong> last stage to probabilities <strong>in</strong><strong>the</strong> primitive, rough underst<strong>and</strong><strong>in</strong>g <strong>of</strong> that term 6 .To put it o<strong>the</strong>rwise, <strong>the</strong>re is no o<strong>the</strong>r way out except turn<strong>in</strong>g to <strong>the</strong>pattern <strong>of</strong> one series, i. e. to <strong>the</strong> Mises model <strong>of</strong> stability <strong>of</strong>frequencies. If you wish, <strong>the</strong> Mises def<strong>in</strong>ition <strong>of</strong> probability is exactly<strong>the</strong> turn to probabilities <strong>in</strong> <strong>the</strong> primitive rough underst<strong>and</strong><strong>in</strong>g <strong>of</strong> thatterm. Accord<strong>in</strong>g to common sense, <strong>the</strong> turn to <strong>the</strong> last stage should bedone <strong>in</strong> such a manner that <strong>the</strong> probabilities <strong>of</strong> <strong>the</strong> highest rank<strong>in</strong>cluded <strong>in</strong> <strong>the</strong> ma<strong>the</strong>matical model <strong>of</strong> <strong>the</strong> given experiments were<strong>in</strong>deed actually measured <strong>in</strong> that experiment. It is apparently difficultto warrant <strong>the</strong> imag<strong>in</strong>ation <strong>of</strong> probabilities <strong>of</strong> even one superfluousrank. Never<strong>the</strong>less, such imag<strong>in</strong>ation is one <strong>of</strong> <strong>the</strong> fundamentals <strong>of</strong> <strong>the</strong>method <strong>of</strong> ma<strong>the</strong>matical statistics.3.6.1. Postulate <strong>of</strong> <strong>the</strong> existence <strong>of</strong> a distribution <strong>of</strong> probabilitiesfor <strong>the</strong> <strong>in</strong>itial r<strong>and</strong>om variables. All <strong>the</strong> considerations <strong>in</strong>ma<strong>the</strong>matical statistics usually beg<strong>in</strong> by postulat<strong>in</strong>g <strong>the</strong> existence, <strong>and</strong>sometimes even <strong>the</strong> concrete type <strong>of</strong> <strong>the</strong> distribution <strong>of</strong> probabilitiesfor unpredictable magnitudes, <strong>the</strong>n <strong>the</strong> estimation <strong>of</strong> density orparameters <strong>of</strong> <strong>the</strong> objectively exist<strong>in</strong>g distribution is dem<strong>and</strong>ed. TheFisherian <strong>the</strong>ory <strong>of</strong> estimation is constructed accord<strong>in</strong>g to this patternas also <strong>the</strong> method <strong>of</strong> maximal likelihood, <strong>the</strong> <strong>the</strong>ories <strong>of</strong> confidence<strong>in</strong>tervals, <strong>of</strong> order statistics etc 7 . An alternative (see Chapter 2) is toconcentrate on empirical justification <strong>of</strong> predictions <strong>of</strong> statisticalstability.The most difficult <strong>and</strong> <strong>in</strong>terest<strong>in</strong>g problem <strong>of</strong> empirically<strong>in</strong>vestigat<strong>in</strong>g statistical stability is rapidly sped by. Here is Grekova’scritical remark (1976, p. 111) about calculat<strong>in</strong>g a confidence <strong>in</strong>tervalwhen <strong>the</strong> number <strong>of</strong> trials is small:128

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