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41.
The binary derivative has been used to measure the randomness of a binary string formed by a pseudorandom number generator for use in cipher systems. In this paper we develop statistical properties of the binary derivative and show that certain types of randomness testing in binary derivatives are equivalent to well-established tests for randomness in the original string. A uniform method of testing randomness in binary strings is described based on using the binary derivative. We show that the new tests are faster and more powerful than several of the well-established tests for randomness. 相似文献
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Human neonates exhibit individually distinctive patterns of variation—sometimes called cry “signatures”—in the acoustics of their cries. For tests of group differences (e.g., age, health status, or ambient language differences), the uniqueness of cry sounds to individuals means that multiple cries from same infant cannot appropriately be treated as independent events for analysis. This approach violates the assumption of independence that underlies many statistical techniques and runs the risk of uncovering “significant” group effects that do not actually exist. Nonetheless, publications continue to appear in which multiple cries from the same infant have been treated as independent events for analysis. To demonstrate the perils, we have compared the cries of infants born into a Mandarin Chinese language environment with cries of infants born into an American English language environment. We show (1) that treating each cry sound as an independent event yields numerous “significant” group effects and (2) that these effects all but disappear when cries are treated appropriately, as “nested” within individual infants. The latter outcome is in keeping with prevailing models of neonatal cry production and casts doubt on the claim that neonates alter their cries to match features of the language spoken in their environment. 相似文献
45.
Karl Gustafson 《Journal of Statistical Computation and Simulation》2015,85(13):2682-2692
Randomness in financial markets has been recognized for over a century: Bachelier (1900), Cowles (1932), Kendall (1953), and Samuelson (1959). Risk thus enters into efficient portfolio design: Fisher (1906), Williams (1936), Working (1948), Markowitz (1952). Reward versus risk decisions then depend upon utility to the investor: Bernoulli (1738), Kelly (1956), Sharpe (1964), and Modigliani (1997). Returns of a portfolio adjusted to risk are measured by a number of ratios: Treynor, Sharpe, Sortino, M2, among others. I will propose a refinement of such ratios. This possibility was mentioned in my recent book: Antieigenvalue analysis, World-Scientific (2011). The result is a new set of growth-to-return risk-based financial ratios of ratios. 相似文献
46.
A substantial body of risk research indicates that women and men differ in their perceptions of risk. This paper discusses how they differ and why. A review of a number of existing empirical studies of risk perception points at several problems, regarding what gender differences are found in such studies, and how these differences are accounted for. Firstly, quantitative approaches, which have so far dominated risk research, and qualitative approaches give different, sometimes even contradictory images of women's and men's perceptions of risk. Secondly, the gender differences that appear are often left unexplained, and even when explanations are suggested, these are seldom related to gender research and gender theory in any systematic way. This paper argues that a coherent, theoretically informed gender perspective on risk is needed to improve the understanding of women's and men's risk perceptions. An analysis of social theories of gender points out some relations and distinctions which should be considered in such a perspective. It is argued that gender structures, reflected in gendered ideology and gendered practice, give rise to systematic gender differences in the perception of risk. These gender differences may be of different kinds, and their investigation requires the use of qualitative as well as quantitative methods. In conclusion, the arguments about gender and risk perception are brought together in a theoretical model which might serve as a starting point for further research. 相似文献
47.
Throughout the world, marriages in which the husband is older than his wife are more common than same-age and women-older marriages. Yet there is surprisingly little systematic knowledge about within-country variation in spousal age differences. This study used comprehensive Swedish register data to investigate how age differences in newly married couples were associated with spouses' age, gender, education, income, and birthplace. Among both women and men, small age differences were most common among the highly educated, high-income earners, and native Swedes, whereas persons with low education, low income, and non-Swedish origin more often entered marriages with large age differences, particularly men-older marriages. Findings are discussed in relation to theoretical attempts to explain spousal age differences and sociodemographic selection into couples with different age relationships. 相似文献
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There has been much recent work on Bayesian approaches to survival analysis, incorporating features such as flexible baseline hazards, time-dependent covariate effects, and random effects. Some of the proposed methods are quite complicated to implement, and we argue that as good or better results can be obtained via simpler methods. In particular, the normal approximation to the log-gamma distribution yields easy and efficient computational methods in the face of simple multivariate normal priors for baseline log-hazards and time-dependent covariate effects. While the basic method applies to piecewise-constant hazards and covariate effects, it is easy to apply importance sampling to consider smoother functions. 相似文献
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Paul Gustafson 《Sociological focus》2013,46(1):3-9
Abstract For approximately one decade after the 1954 Brown v. Topeka decision, there were few governmental pressures censuring school systems which maintained racial segregation. The Civil Rights Act of 1964 and a variety of encompassing federal court decisions in the late 1960s challenged and overturned the dual school system in the South and many segregationist practices in the North. Quantitative data concerning the within-district racial segregation of teachers and students in 143 school systems are examined. The governmental activities integrated teaching staffs and greatly reduced the segregation of black students from white. Changes were more substantial within the South and, by 1972, racial segregation was less within southern school systems than those in other regions. Because of the residential segregation of the races, schools in many central cities have a different racial composition than those in neighboring suburbs. If the only integration is within a specific school district, present demographic trends may produce a resegregation of students in many metropolises. 相似文献