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101.
When the two-sample t-test has equal sample slies, it is widely considered to be a robust procedure (with respect to the significaoce level) under violatioa of the assuaptioo of equal variances. This paper is coa-earned with a quantification of the amount of robustness which this procedure has under such violations, The approach is through the concept of "religion of robustness" and the resluts show an extremely strong degree of robustness for the equal an extremely strong degree of robustness for the equal sample size t-test, probably more so than most statistyicians realise. This extremely high level of robustness, however, reduces quickly as the sample sizes begin to vary from equality. The regions of robustnes obtained show that while most users would likely be satisfied with the degree of robustness inherent when the two sample sizes each vary by 10% from equality, most would wish to be much more cautions when the variation is 20%. The study covers sample sizes n1 -= n 2 = 5(5)30(10)50 plus 10% and 20% variations thereof for the two-tailed test and nominal significance levels of 0.01 and 0.05. 相似文献
102.
We compared the robustness of univariate and multivariate statistical procedures to control Type I error rates when the normality and homocedasticity assumptions were not fulfilled. The procedures we evaluated are the mixed model adjusted by means of the SAS Proc Mixed module, and Bootstrap-F approach, Brown–Forsythe multivariate approach, Welch–James multivariate approach, and Welch–James multivariate approach with robust estimators. The results suggest that the Kenward Roger, Brown–Forsythe, Welch–James, and Improved Generalized Aprroximate procedures satisfactorily kept Type I error rates within the nominal levels for both the main and interaction effects under most of the conditions assessed. 相似文献
103.
We investigate the effect of group versus individual decision-making in the context of risky investment decisions in which
all subjects are fully informed of the probabilities and payoffs. Although there is full information, the lottery choices
pose cognitive challenges so that people may not be sure of their expected utility-maximizing choice. Making such decisions
in a group context provides real-time information in which group members can observe others’ choices and revise their own
decisions. Our experimental results show that simply observing what others in the group do has a significant impact on behavior.
Coupling real-time information with group decisions based on the median value, i.e., majority rule, makes the median investment
choice focal, leading people with low values to increase investments and those with high values to decrease investments. Group
decisions based on the minimum investment amount produce more asymmetric effects. 相似文献
104.
105.
Patricia Canto Jesús Benítez Granados Mónica Adriana Martínez Ramírez Edgardo Reyes Guillermo Feria-Bernal Eduardo García-García 《The aging male》2016,19(3):187-191
Mitochondrial defects have been related to obesity and prostate cancer. We investigated if Mexican–Mestizo men presenting this type of cancer, exhibited somatic mutations of ATP6 and/or ND3.Body mass index (BMI) was determined; the degree of prostate cancer aggressiveness was demarcated by the Gleason score. DNA from tumor tissue and from blood leukocytes was amplified by the polymerase chain reaction and ATP6 and ND3 were sequenced. We included 77 men: 20 had normal BMI, 38 were overweight and 19 had obesity; ages ranged from 52 to 83. After sequencing ATP6 and ND3, from DNA obtained from leukocytes and tumor tissue, we did not find any somatic mutations. All changes observed, in both genes, were polymorphisms. In ATP6 we identified, in six patients, two non-synonymous nucleotide changes and in ND3 we observed that twelve patients presented non-synonymous polymorphisms. To our knowledge, this constitutes the first report where the complete sequences of the ATP6 and ND3 have been analyzed in Mexican–Mestizo men with prostate cancer and diverse BMI. Our results differ with those reported in Caucasian populations, possibly due to ethnic differences. 相似文献
106.
The current study examined the effectiveness of the Prevention and Relationship Enhancement Program (PREP) with lower-income and racial/ethnic minority (African American and Latino/a) couples. Additionally, we tested whether relationship outcomes varied based on the delivery format (i.e., group format vs. couple format). The sample included 321 unmarried couples expecting a child or who have a child 3 month old or younger. The couples participated in 16 hr of PREP via a group or a couple format over the course of 2-3 months. Couples relationship quality was assessed prior to and directly after the program. The results showed that men and women demonstrated significant gains in their communication skills, relationship functioning, friendship, dedication, and relationship confidence. Couples who participated in PREP via the couple format had better outcomes on three of the seven relational outcomes as compared to couples who participated in PREP via the group format. 相似文献
107.
Kelley Quirk Johanna Strokoff Jesse J. Owen Tiffany France Carrie Bergen 《Journal of marital and family therapy》2014,40(4):442-453
Couple relationship education (CRE) programs are intended to prevent negative couple outcomes, however, some evidence suggests couples in greater distress may still benefit. The current study examined pre‐ and postchanges in relationship functioning of 362 low‐income African American and Hispanic couples. Outcomes (dedication and communication) were assessed by examining differences between two distinct groupings of couples; distressed (both partners reporting clinically significant distress) and nondistressed (neither partner reporting clinically significant distress) couples. Distressed couples at predemonstrated large‐sized gains in all outcome variables, as compared to nondistressed couples. Those who participated in the single‐couple format demonstrated lower gains in positive communication as compared to those in the group format. Implications for distressed couples in CRE programs are offered. 相似文献
108.
Existing ethical discussion considers the differences in care for identified versus statistical lives. However, there has been little attention to the different degrees of care that are taken for different kinds of statistical lives. Here we argue that for a given number of statistical lives at stake, there will sometimes be different, and usually greater, care taken to protect predictable statistical lives, in which the number of lives that will be lost can be predicted fairly accurately, than for unpredictable statistical lives, where the lives are at stake because of a low‐probability event, such that most likely no one will be affected by the decision but with low probability some lives will be at stake. One reason for this difference is the statistical challenge of estimating low probabilities, and in particular the tendency of common approaches to underestimate these probabilities. Another is the existence of rational incentives to treat unpredictable risks as if the probabilities were lower than they are. Some of these factors apply outside the pure economic context, to institutions, individuals, and governments. We argue that there is no ethical reason to treat unpredictable statistical lives differently from predictable statistical lives. Moreover, lives that are unpredictable from the perspective of an individual agent may become predictable when aggregated to the level of a societal decision. Underprotection of unpredictable statistical lives is a form of market failure that may need to be corrected by altering regulation, introducing compulsory liability insurance, or other social policies. 相似文献
109.
110.
Appropriate measurement of competitive balance is central to the economic analysis of professional sports leagues. We examine the distributional properties of the ratio of standard deviations (RSD) of points percentages, the most widely used measure of competitive balance in the sports economics literature, in comparison with other standard‐deviation‐based measures. Simulation methods are used to evaluate the effects of changes in season length on the distributions of competitive balance measures for different distributions of the strengths of teams in a league. The popular RSD measure performs as expected only in cases of perfect balance; if there is imbalance in team strengths, its distribution is sensitive to changes in season length. It is therefore not recommended for comparisons of competitive balance for different sports leagues with different numbers of teams and/or games played. (JEL L83, D63, C63) 相似文献