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A model for the distribution of security price changes is proposed. The model is similar to previous analyses of stock market price behavior in that logged price changes are assumed to be independent (random walk models). However, this model differs from earlier work in that the logged price changes are not assumed to follow some stable distribution (which might possibly be normal). Instead, the logged price changes are assumed to follow a distribution that is a Poisson mixture of normal distributions. It is shown that the analytical characteristics of such a distribution agree with what has been found empirically. That is, this distribution is in general skewed, leptokurtic, more peaked at its mean than the distribution of a comparable normal variate, and has greater probability mass in its tails than the distribution of a comparable normal variate. A cumulant matching method is suggested for estimating the four parameters of the distribution. The model is also generalized to the multivariate case in which a group of securities may be studied simultaneously. Parameters are estimated in a manner analogous to that of the univariate case. A brief frequency discussion of the spectrum for the univariate case is also provided. Finally, a univariate empirical study of ten of the flow Jones Industrial stocks is presented. All parameters are estimated, and graphs are provided to show how actual prices varied from 1926-1960. These graphs are compared with the model trend (linear), with a one standard deviation confidence region. For each stock, two graphs of the cumulative distribution function (c.d.f.) of the price differences are presented. One, the empirical c.d.f. is computed directly from the sample observations. The other, the "estimated" theoretical c.d.f., is computed by substituting the parameter estimates for the true parameters in the proposed model. Agreement between the two curves is often quite dose. The numerical results must be interpreted bearing in mind that the sample sizes may be much too small to provide efficient estimators, and the time periods studied may be much too long to yield small confidence bounds on the price variations that should be expected at reasonable significance levels. [ABSTRACT FROM AUTHOR]

Pseudo-random sequences can be computed to approximate a distribution or a sample correlation function. How ever, conventional techniques do not allow the control of both distribution and correlation, except for a few special cases. This paper presents a more general and more accurate procedure, based on correlation transfer, to generate a pseudo-random set with select ed distribution and correlation. Two sets are com puted, an ordered set in which the sample values cor respond to the desired probability distribution and an auxiliary set with the desired correlation and arbi trary distribution. The auxiliary set provides the addresses to scramble the ordered set. Thus, the desired correlation is injected without changing the distribution. The representation of continuous and discrete distributions is optimum for a specified set size. An example illustrates the method. [ABSTRACT FROM PUBLISHER]

Several letters to the editor are presented in response to the articles published in the previous issues including "Bound and Free Water in Hydrophilic Fibers as Indicated by X-band Microwave Absorption," "The Application of the First and Third Asymptotic Distributions to Abrasion Fatigue and Repeated Extension of Yarns and to Bending of Fabrics," by H. P. Stout, "A Rapid Method of Measuring Yarn Diameters," by G. R. Wray.

The rate of dissolution of spheroidized FeC in ferrite in both high purity and commercial purity plain carbon eutectoid steels has been investigated. The experiments consisted of equilibrating wire specimens of spheroidized eutectoid steels at 650°C or 700°C and then jumping the temperature (in 2 to 7 m-sec) 4 to 32 C deg above the equilibration temperature. After heating, the specimens were maintained constant at the new temperature, and the dissolution of FeC was followed by observing the changes in electrical resistivity. The data are correlated to changes in the average carbon concentration in ferrite and are compared to the predictions of a generalized phenomenological model. Two important facts have been determined. First, the FeC ferrite interfaces are not in a state of local equilibrium during dissolution; the deviations from equilibrium in all cases were large. Second, the kinetics of dissolution are first order and the log of the reaction rate constants are a linear function of (1/ T), where T is the absolute temperature. These results lead to the conclusion that under the present experimental conditions, the dissolution of FeC in ferrite is controlled entirely by an interfacial reaction. A rather detailed description of the experimental procedure is included in this paper because the technique is new, and it is broadly applicable in the study of many metallurgical phenomena. [ABSTRACT FROM AUTHOR]

This paper takes a few steps toward alleviating problems of data analysis that arise from the fact that elementary expressions for density and cumulative distribution functions (c.d.f.'s) for most stable distributions are unknown. In section 2 results of Bergstrom [3] are used to develop numerical approximations for the c.d.f.'s and the inverse functions of the c.d.f.'s of symmetric stable distributions. Tables of the c.d.f.'s and their inverse functions are presented for twelve values of the characteristic exponent. In section 3 the usefulness of the numerical c.d.f.'s and their inverse functions in estimating the parameters of stable distributions and testing linear models involving stable variables is discussed. Finally, section 4 presents a Monte Carlo study of truncated means as estimates of location. In every case but the Gaussian, some truncated mean is shown to have smaller sampling dispersion than the full mean. [ABSTRACT FROM AUTHOR]

This article reports on how the eruption of permanent teeth is affected by environmental factors. The article discusses the sequence in which permanent teeth develop, noting that it can be altered due to caries prevalence. Information is also provided on dentition, deciduous teeth, and the role of age in tooth development.