Effect of violation of normality on the t test of the correlation coefficient.

Performed simulations to study the effects of violations of the normality assumption on the t test of the Pearson product-moment correlation coefficient. The test was robust as long as the variables were independent, even with violations in combined distributions. Large effects for violations of normality were found when the variables were not independent, even though the population correlation was zero. (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison of the power of the paired samples t test to that of Wilcoxon's signed-ranks test under various population shapes.

Used Monte Carlo methods to assess the relative power of the paired-samples t test and Wilcoxon's signed-ranks test (WSR) under 10 population shapes. Results indicate that each statistic was more powerful than the other in given situations; power advantages of the t under normal theory were small; in nonnormal situations, the t test never attained more than modest advantages. The WSR was more often the more powerful test, and the magnitude of the WSR's power advantage often increased with sample size. It is concluded that the claim that parametric tests are more powerful than nonparametric tests is not justified. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rank transformations and the power of the Student t test and Welch t' test for non-normal populations with unequal variances.

In the present computer simulation study, the Student t test and the Welch version of the t test (the t′ test) were performed first on the initial sample values and then on ranks of the sample values. Unequal variances together with unequal group sizes markedly altered the probability of Type 1 and Type 2 errors for normal and for 8 kinds of nonnormal distributions, including mixed-normal, exponential, lognormal, and Cauchy distributions. Substitution of the Welch t′ test for the Student t test eliminated effects of unequal variances, but not effects of non-normality. The t test on ranks, which is equivalent to the Mann-Whitney-Wilcoxon test, was more powerful than the Student t test for several nonnormal distributions, but exhibited a substantial power loss when variances were unequal. The Welch t′ test in conjunction with the rank transformation simultaneously counteracted effects of both nonnormality and unequal variance. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Power of the independent samples t test under a prevalent psychometric measure distribution.

Studies in psychology often have low power because of inadequate sample size. Thus, recent articles in the Journal of Consulting and Clinical Psychology have suggested making sample size determinations through readily available tables that are based on population normality. Questions have been raised on the use of these power tables because prevalent psychometric distributions, such as the discrete mass at zero with gap that occurs with 1st use or onset variables, are radically nonnormal. In addition to demonstrating the robustness of the independent samples t test with respect to Type I error, the major finding of this study shows that researchers may use these power tables without modification for this radically nonnormal distribution. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The robustness of test statistics to nonnormality and specification error in confirmatory factor analysis.

Monte Carlo computer simulations were used to investigate the performance of three χ–2 test statistics in confirmatory factor analysis (CFA). Normal theory maximum likelihood χ–2 (ML), Browne's asymptotic distribution free χ–2 (ADF), and the Satorra-Bentler rescaled χ–2 (SB) were examined under varying conditions of sample size, model specification, and multivariate distribution. For properly specified models, ML and SB showed no evidence of bias under normal distributions across all sample sizes, whereas ADF was biased at all but the largest sample sizes. ML was increasingly overestimated with increasing nonnormality, but both SB (at all sample sizes) and ADF (only at large sample sizes) showed no evidence of bias. For misspecified models, ML was again inflated with increasing nonnormality, but both SB and ADF were underestimated with increasing nonnormality. It appears that the power of the SB and ADF test statistics to detect a model misspecification is attenuated given nonnormally distributed data. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Justifying the use and increasing the power of a t test for a randomized experiment with a convenience sample.

The standard error in an independent-groups t test is usually derived assuming that individuals are randomly sampled from populations of infinite size. However, t tests are routinely used in randomized experiments with individuals obtained from convenience samples. In such cases, the use of a t test is most often justified by supposing (a) that the convenience sample was a random sample from a hypothetical infinite population and (b) that it is this hypothetical population to which inference is being drawn. It is shown how the use of a t test with a convenience sample can be justified without reference to a hypothetical infinite population and how it may be possible to modify the t test to increase its power for drawing inferences in randomized experiments. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Validity generalization and situational specificity: A second look at the 75% rule and Fisher's z transformation.

We analyzed the James, Demaree, and Mulaik (1986) critique of validity generalization, contending that the work (a) is not relevant to the real-world use of validity generalization in organizations, (b) has overlooked the bulk of the evidence against the situational specificity hypothesis, and (c) has confused the processes of hypothesis testing and parameter estimation in validity generalization and has made incorrect statements about the assumptions underlying both. In addition, the critique of the 75% rule is a statistical power argument; the procedures for use of confidence intervals are erroneous; there is no double correction of artifacts in validity generalization; the bias in the correlation (r) and the sampling error formula for r is well-known, trivial in magnitude, and has no empirical significance; and the use of the Fisher's z transformation of r in validity generalization studies and other meta-analyses creates an unnecessary inflationary bias in estimates of true validities and provides no benefits. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A second look at the personality/disease specificity hypothesis: A response to Friedman and Booth-Kewley.

While presenting persuasive evidence of the functional integrity of an interactive mind/body system, H. S. Friedman and S. Booth-Kewley's (see record 1987-31704-001) meta-analysis of the personality/disease relationship does injury to the specificity hypothesis, which contends that there may be emotion-specific/disease-specific linkages in the etiology and progress of certain stress-responsive syndromes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Review of Optimizing work performance: A look beyond the bottom line.

Reviews the book, Optimizing work performance: A look beyond the bottom line by Martin Morf (1986). This book is an interesting addition to the rapidly growing list of publications which deal with "improving performance" or "increasing productivity" in the workplace. It is an addition, however, for which an appropriate audience may be difficult to find. Indeed, in attempting to be "of particular interest to those involved in personnel, corporate organization, or industrial relations, as well as to scholars and students of organizational psychology", the book may fail to appeal strongly to any of these groups. This is unfortunate because Martin Morf makes a number of interesting comments in his book--particularly about the relationship between the individual, his or her work, and society. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Associative learning changes intrinsic to Hermissenda Type A photoreceptors.

The eyes of the nudibranch mollusc Hermissenda contain 2 classes of photoreceptors. Type B photoreceptors exhibit increased light responses (LRs) and membrane excitability after repeated pairings of light and rotation and play an important role in the mediation of associatively produced reductions in phototactic behavior. Type A photoreceptors (TAPs) have also been shown to change with associative training. In previous research it was not possible to determine whether the effects of associative training reflected changes in synaptic input to TAPs or intrinsic changes in somatic conductances. In the present study, intracellular recordings from synaptically isolated TAPs were obtained on retention days after training, and pairing-specific decreases in light-induced generator potentials and decreases in resting input resistance were observed. Current- and voltage-clamp analysis of TAPs from untrained animals revealed that an important determinant of the steady-state LR was a calcium-activated K+ current (IK–Ca). Thus, TAPs also appear to be a primary site for associative information storage in Hermissenda. It is suggested that enhancement of IK–Ca by associative training may contribute to the diminished LR of TAPs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Type I error rate of the chi-square test in independence in R?×?C tables that have small expected frequencies.

Sampling experiments are reported that show that the uncorrected chi-square test of independence is exceptionally robust with respect to small expected frequencies in R?×?C contingency tables. In general, error rates that exceed .06 occurred only when both marginal probability distributions were extremely skewed and sample size was small. Nevertheless, the quality of the approximation of chi-square probabilities for exact multinomial probabilities was sometimes poor, although excessive errors in approximation by W. G. Cochran's (1952) criteria usually resulted from actual error rates being smaller, not larger, than the nominal level. A distinction is made between accuracy of approximation and control of the Type I error rate as considerations dictating the advisability of using an approximate test. (38 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A test of the fail-safe N for self-help programs.

A meta-analysis of published studies on the clinical efficacy of selected self-help programs (F. Scogin et al; see record 1990-15222-001) indicated that such conditions were more effective than no-treatment controls. Calculation of a fail-safe N showed that 53 nonsignificant studies would have to exist to render the conclusions of the meta-analysis invalid. Results indicate that unpublished research is unlikely to threaten the validity of the original meta-analysis. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Psychologists and technology: A look at the future.

A randomly sampled group of 213 California psychologists were interviewed to assess their use of practice technology and their general attitudes toward technology. Results indicated that (a) nearly 3/4 were using a computer in their practice; however, nearly all uses involved little more than word processing; (b) 1/4 had used a modem to connect to an on-line service (substantially higher than comparable data from business professionals); (c) over 3/4 were using a fax machine in their practice; (d) 1/2 used a pager; (e) 4 out of 10 used a computerized voice mail system, mostly in combination with other messaging systems; (f) few were using computerized assessments; and (g) over half rated themselves as mildly to highly technophobic. Hierarchical multiple regression analyses indicated that technophobia, use of psychological assessment instruments, age, and percentage of managed care clients predicted the use of computer applications. Results are discussed in terms of their practice implications for psychologists (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A more appropriate test of the Kuhnian displacement thesis.

Evaluated the conclusion of P. C. Friman et al (see record 1993-39713-001) that cognitive psychology has not displaced behavioral psychology and psychoanalysis as the dominant paradigm in psychology. The frequency with which 4 preeminent general publications in psychology cited articles published in the 4 leading journals in cognitive psychology, in behavioral psychology, and in psychoanalysis between 1977 and 1992 was examined. In contrast to the findings of Friman et al, results suggest that cognitive psychology is flourishing while the other 2 schools are languishing in comparison. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Beyond global sociosexual orientations: A more differentiated look at sociosexuality and its effects on courtship and romantic relationships.

Sociosexuality is usually assessed as the overall orientation toward uncommitted sex, although this global approach may mask unique contributions of different components. In a large online study (N = 2,708) and a detailed behavioral assessment of 283 young adults (both singles and couples) with a 1-year follow-up, the authors established 3 theoretically meaningful components of sociosexuality: past behavioral experiences, the attitude toward uncommitted sex, and sociosexual desire (all measured by a revised version of the Sociosexual Orientation Inventory). Discriminant validity was shown with regard to (a) their factorial structure, (b) sex differences, (c) many established correlates of sociosexuality, and (d) the prediction of observed flirting behavior when meeting an attractive opposite-sex stranger, even down to the level of objectively coded behaviors, as well as (e) the self-reported number of sexual partners and (f) changes in romantic relationship status over the following year. Within couples, the 3 components also showed distinct degrees of assortative mating and distinct effects on the romantic partner. Implications for the evolutionary psychology of mating tactics are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A new look at the effects of noise: A rejoinder.

Outlines a composite theory to account for the effects of noise upon performance. The 4 main determinants are (a) masking, both of acoustic cues and of inner speech; (b) distraction; (c) a beneficial increase in arousal when the noise begins, which gradually lessens and falls below normal to produce a decrement in performance when the noise stops; and (d) positive and negative transfer from noise to quiet. Positive transfer results from the more effective learning of the task in noise under the influence of the increase in arousal. Negative transfer results from the techniques of performance used in noise to counteract the masking or distraction, when they are not appropriate in quiet. (49 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evidence for the Type in Type A behavior: A taxometric analysis.

Four taxometric procedures were applied to the self-report responses of 1,239 Ss who completed the Jenkins Activity Survey (JAS). All 4 procedures provided clear evidence for a latent class variable. A continuous model simulation that mimicked the item characteristics of the JAS correctly rejected the presence of a latent class variable. Using an external validation procedure, I reexamined 5 previously published studies to determine if the simple Type A–B dichotomy was as predictive of outcome measures as the use of continuous JAS scores. The presence of a latent class variable predicts no gain in predictive power in moving from a simple dichotomy to continuous scores. Across 5 studies, there was a slight decrease in the size of the relation between Type A-B and outcome for the continuous JAS scores relative to the simple Type A-B dichotomy. Taken together, these results suggest that the Type A-B distinction is based on a latent typology. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Review of Introduction to testing and the use of test results in public schools.

Reviews the book, "Introduction to testing and the use of test results in public schools," by Arthur E. Traxler, Robert Jacobs, Margaret Selover, and Agatha Townsend (see record 1954-01580-000). This book is designed to serve as a "practical, down-to-earth handbook for schools beginning the use of objective tests, for teacher discussion groups, for in-service training programs, for persons who have had experience with tests but who desire to brush up on the simpler fundamentals of testing, and for introductory classes in tests and measurements." This brief, nontechnical book should be distinctly useful to the groups of readers toward whom it is directed. Despite its title, the revision seems equally appropriate for public and independent schools. From the standpoint of the former, the more detailed discussions of test selection and program planning included in the revised edition should be of particular interest. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Three-dimensional reconstruction of curves from pairs of projection views in the presence of error. II. Analysis of error

We have previously described an approach to 3D intracerebral vascular reconstruction that uses an MRA as a reconstruction base. Additional vessels seen only by angiography are added by segmenting 2D curves from projection angiograms and reconstructing these curves into 3D, building upon the MRA. This paper is the second of two that discuss the specific problem of reconstructing a 3D curve from a given pair of 2D curves in the presence of error. The method presented is capable of detecting and handling many errors produced by misregistration, image distortion, or misdefinition of 2D curves. The first paper gives an algorithm. The current paper discusses factors affecting the accuracy of a reconstructed curve, with emphasis upon registration error. We analyze the spatial accuracy of a reconstructed point in terms of the relationships between pixel size, relative viewing angle, 3D point location, and registration error. We provide a theoretical framework that, given the known error properties of a registration algorithm, allows optimization of the viewing geometry so as to produce the highest precision of point reconstruction. A major focus is the effect of registration error upon the reconstruction of a curve. We subdivide registration error into two types, one of which produces smoothly continuous point placement errors and the other of which produces pixel pairing errors. We test our ability to reconstruct a 3D curve in the presence of both. Finally, we summarize approaches to other sources of error. We conclude with a list of recommendations to optimize reconstruction accuracy. When projection points are associated by the rules of epipolar geometry, viewplane point displacements should not exceed 1.5-2 mm along the axis perpendicular to epipolar planes.