A mathematical model of HIV/sexually transmitted infections (STI) transmission was used to examine how linearity or nonlinearity in the relationship between the number of unprotected sex acts (or the number of sex partners) and the risk of acquiring HIV or a highly infectious STI (such as gonorrhea or chlamydia) affects the utility of sexual…

Statistical approaches to assess how prevention and intervention programs achieve their effects are described and illustrated through the evaluation of a health promotion program to reduce dietary cholesterol and a school-based drug prevention program. Analyses require the measurement of intervening or mediating variables to represent the…

The problem associated with evaluating an econometric model using values outside those used in the model estimation is illustrated in the evaluations of a residential load management program during each of two successive years. Analysis reveals that attention must be paid to this problem. (Author/TJH)

A general model for prediction and association is described for the situation in which both criterion and predictor(s) are discrete variables. The approach can be employed for the general case involving any number of predictors, and the related measures of multiple and partial association are described. (Author/GK)

A technique to estimate variances of weighted estimates in program evaluation is discussed. BRR estimates of variance are constructed from orthogonally weighted subsamples and can provide better estimates from complex samples than can other methods. Use of BRR is illustrated in a government evaluation of a food service program. (SLD)

The authors demonstrate how exponential smoothing can play a role in the identification of the intervention component of an interrupted time-series design model that is analogous to the role that the sample autocorrelation and partial autocorrelation functions serve in the identification of the noise portion of such a model. (Author/BW)

One source of bias, regression artifacts, in program evaluations that use regression discontinuity design is identified, and its importance is discussed. A method is suggested for its correction. Although use of this method does not solve the problem of selection bias, it does improve the reliability of nonexperimental methods. (SLD)

To solve an applied research problem with bipolar data, a set of equations was developed that combined all plus and minus data combinations into unique values and scale points. The equations were tested through computer simulations and empirical tests. Resulting index scores were approximately interval and linear and easy to use and interpret.…

Selectivity problems are discussed in terms of a general model that is estimated by the maximum likelihood method. Both single-group and multiple-group analyses are considered. An extension of the general model to latent variable models is discussed. (Author/PN)

The use of analysis of variance was examined under the assumption that the treatment had been randomly assigned to students, when in fact, the class had been the unit. Data support the idea that if one can randomly assign treatments to intact classes, consideration should certainly be given to doing so. (Author/GK)

Current practices of reporting a single mean intercoder agreement in meta-analysis leads to systematic bias and overestimates reliability. An alternative is recommended in which average intercoder agreement statistics are calculated within clusters of coded variables. Two studies of intercoder agreement illustrate the model. (SLD)

In this analysis of 1,815 arbitration cases in British Columbia in 1982-85, bias is identified in the bivariate estimates of the probability of management wins by industry and issue. Bivariate estimate errors in these cases can result from failure of estimates to adjust for the effects of omitted variables. (TJH)

A two-step procedure is developed for the analysis of pretest-posttest data. Nonlinear canonical correlation analysis is followed by covariance analysis of optimally scaled pretest and posttest measures. The procedure is available in the computer program CANALS. Advantages of the two-step procedure are discussed. (SLD)

Prediction of success in a special program often guides program participant selection and treatment. If the statistical analysis used to develop such predictions is based on the special selectivity built into the program, the predictions can be misleading and the validation tests uninformative. Federal district court pretrial release data is used…

A method is presented for analyzing data collected in a multiple group time-series design. This consists of testing linear hypotheses about the experimental and control group-means. Both a multivariate and a univariate procedure are described. (Author/GK)