Partial and part correlations are discussed as a means of statistical control. Partial and part correlation coefficients measure relationships between two variables while controlling for the influences of one or more other variables. They are statistical methods for determining whether a true correlation exists between a dependent and an…

All parametric statistical analyses have certain assumptions about the data that must be met reasonably to warrant the use of a given analysis. Distributional normality, for example, is a common assumption. There is a variety of ways that data in a distribution may detract from normality, but one common problem is the presence of outliers. Many…

Homoscedasticity is an important assumption of linear regression. This paper explains what it is and why it is important to the researcher. Graphical and mathematical methods for testing the homoscedasticity assumption are demonstrated. Sources of homoscedasticity and types of homoscedasticity are discussed, and methods for correction are…

Two approaches to regression-based reading-level-match research designs, one of which used matched Rasch-scaled "w" scores, were tested with 544 primary grade children of different reading levels. Results call into question the conclusion that orthographic skills are compensatory for reading-disabled children. (SLD)

Discusses assumptions of multiple regression that are not robust to violation: linearity, reliability of measurement, homoscedasticity, and normality. Stresses the importance of checking assumptions. (SLD)

Asserts that, in principle, an analyst should be satisfied with infinite estimates slope in logistic regression because it indicates that a predictor is perfect. Using simple approaches, hypothesis tests may be performed and confidence intervals calculated even when a slope is infinite. Some functions of parameters that are infinite are still…

Notes that existence of substantial correlation between two or more independent variables creates problems of multicollinearity in multiple regression. Discusses multicollinearity problem in social work research in which independent variables are usually intercorrelated. Clarifies problems created by multicollinearity, explains detection of…

Discusses a regression model for the analysis of longitudinal count data in a panel study by adapting an integer-valued first-order autoregressive (INAR(1)) Poisson process to represent time-dependent correlation between counts. Derives a new negative multinomial distribution by combining INAR(1) representation with a random effects approach.…

Post hoc and planned comparison procedures for interpreting chi-square contingency table test results are presented, and a planned comparison procedure that simplifies the process of creating a contingency table by creating single-degree-of-freedom contrasts through a regression-based approach is proposed. (SLD)

Evaluated the use of Mallow's C(p) and Wherry's adjusted R squared (R. Wherry, 1931) statistics to select a final model from a pool of model solutions using computer generated data. Neither statistic identified the underlying regression model any better than, and usually less well than, the stepwise selection method, which itself was poor for…

Uses examples of hierarchical linear modeling (HLM) at local and national levels to illustrate proper applications of HLM and dummy variable regression. Raises cautions about the circumstances under which hierarchical data do not need HLM. (SLD)

Provides a practical introduction to methods of constructing confidence intervals for multiple and partial "R" squared and related parameters in multiple regression models based on noncentral distributions. Illustrates software use (e.g. the Statistical Package for Social Studies) for confidence intervals and discusses measures of effect…

Speech intelligibility of 24 prelingually deaf pediatric cochlear implant (CI) recipients with 84 months of device experience was investigated. Each CI participant's speech samples were judged by a panel of 3 listeners. Intelligibility scores were calculated as the average of the 3 listeners' responses. The average write-down intelligibility score…

International studies in education provide researchers with opportunities to examine how students with both similar and dissimilar formal education systems perform on a single test and provide rich information about the relationships among student outcomes and the factors that affect them. Using hierarchical linear regression techniques and TIMSS…

The present paper shows that the usual factor analytic structured data dispersion matrix lambda psi lambda' + delta can readily arise from a set of scores y = lambda eta + epsilon, shere the "common" (eta) and "unique" (epsilon) factors have nonzero covariance: gamma = Cov epsilon,eta) is not equal to 0. Implications of this finding are discussed…