Brownian Moton in the Stock Market 147 (NYSE)transaction for a gIven day. He 1s told that these data consti- tute a sample of approximately 1000 from some unknown population, together wnth some of their more important attributes or varables, eleven In all The fact that these eleven were the most important, out of a much larger number obtainable, from annual reports, for example, might be ferred from the fact that this choice of eleven was published every day Our statistician 1s asked to investigate this population, to determine If It 1s a homogeneous sample, and what relations (in the probabIlty sense) exist between the varables or attributes lsted for each member The methods of attacking the raw data on such a problem al nown, especially to biologists, we quote an astronomical reference l4 primarly because of personal famIliarty A common first step 1s the determination of distrbution functions Casual Inspection of the data eveals that of eleven attributes or varables lsted for each member of the population, Six, exclusive of the change, are devoted to something called prce, 'evidently a dominant variable even among those so important 120 Fig 1 Distribution function of prices as to be published every day On learning that close'was the most recent data, our statistician would plot the distrbution function of closing price alone for the 1000 members of the sample(Fig 1) Inspection of Fig shows that closing prices on that day were certainly not normally dis tributed, but the shape suggests that logarithms of prices might beE 1 suggests a loganthmuc-normal distrbution Figure 2 gives the Identical data of Fig 1 wth loge price as independent variable( see refer ence 1, page 9 for numerical methods) At this point our statistician will make a'discovery'and answer one th he questions posed to him A subsIdiary maximum around log Pa4 5 PA$100) In Fig 2 suggests that the population contains at least two sub-groups, 1e, It Is not homogeneous Re-examination of the raw dat around Pas100 reveals an excessive number of our sample wnth the attrbute'pfd'(preferred), and plotting the distribution function of these only gives Fig 3 The remaining members of the population, the common or ordinary ones is plotted n Fig 4 This appears normal, and as a rough