Leona S. Aiken

The Effect of Different Forms of Centering in Hierarchical Linear Models

Multilevel models are becoming increasingly used in applied educational social and economic research for the analysis of hierarchically nested data. In these random coefficient regression models the parameters are allowed to differ over the groups in which the observations are nested. For computational ease in deriving parameter estimates, predictors are often centered around the mean. In nested or grouped data, the option of centering around the grand mean is extended with an option to center within groups or contexts. Both are statistically sound ways to improve parameter estimation. In this article we study the effects of these two different ways of centering, in comparison to the use of raw scores, on the parameter estimates in random coefficient models. The conclusion is that centering around the group mean amounts to fitting a different model from that obtained by centering around the grand mean or by using raw scores. The choice between the two options for centering can only be made on a theoretical basis. Based on this study, we conclude that centering rules valid for simple models, such as the fixed coefficients regression model. are no longer applicable to more complicated models, such as the random coefficient model. We think researchers should be made aware of the consequences of the choice of particular centering options.

The Problem of Units and the Circumstance for POMP.

Many areas of the behavioral sciences have few measures that are accepted as the standard for the operationalization of a construct. One consequence is that there is hardly ever an articulated and understood framework for the units of the measures that are employed. Without meaningful measurement units, theoretical formulations are limited to statements of the direction of an effect or association, or to effects expressed in standardized units. Thus the long term scientific goal of generation of laws expressing the relationships among variables in scale units is greatly hindered. This article reviews alternative methods of scoring a scale. Two recent journal volumes are surveyed with regard to current scoring practices. Alternative methods of scoring are evaluated against seven articulated criteria representing the information conveyed by each in an illustrative example. Converting scores to the percent of maximum possible score (POMP) is shown to provide useful additional information in many cases.

A psychosocial model of sun protection and sunbathing in young women: the impact of health beliefs, attitudes, norms, and self-efficacy for sun protection.

A psychosocial model of sun protection and sunbathing as distinct behaviors was developed on 202 young Caucasian women and replicated in an independent sample (n = 207). Proximal outcomes were intention to sun protect and intention to sunbathe; distal outcomes included sun protection and sunbathing behavior measured 5 months later. Objective risk for skin cancer plus 4 classes of psychosocial variables (sun-protective health beliefs, self-efficacy for sun protection, attitudes toward sunbathing, and norms for sunbathing and sun protection) served as predictors. Sun-protective norms and self-efficacy for sun protection predicted only intention to sun protect; sunbathing norms predicted only intention to sunbathe. Susceptibility and advantages of tanning predicted both intention constructs, which, in turn, predicted behavior. These findings distinguish sun protection from sunbathing and provide a basis for intervention design.

Family Conflict and Children's Internalizing and Externalizing Behavior: Protective Factors

The current investigation examined whether the positive association of family conflict to adolescent depression and conduct problems is attenuated by maternal, paternal, and peer attachment, and maternal and paternal monitoring, within a low-income, multiethnic sample of 284 adolescents. Parental attachment and monitoring moderated the link from family conflict to conduct problems but not depression; the relationships among family conflict, the hypothesized protective factors, and conduct problems were further modified by adolescent gender but not ethnicity. In general, higher levels of the hypothesized protective factors attenuated the relationship between family conflict and conduct problems for girls but exacerbated this relationship for boys. These findings suggest that, in general, parental attachment and monitoring served as protective factors for girls while serving as additional risk factors for boys in conflictual families.

Health Beliefs and Compliance With Mammography-Screening Recommendations in Asymptomatic Women

The utility of the health belief model (HBM) for predicting compliance with the American Cancer Society recommendations for mammography screening over and above demographics, knowledge, physician input, and objective risk for breast cancer was assessed. In all, 615 predominantly middle-class White women, age 35-92, were surveyed in 1987-1989. A multiple indicator measurement model of the HBM constructs of perceived susceptibility, severity, benefits, and barriers was verified with confirmatory factor analysis. Physician input alone accounted for 25% of the variance in compliance; HBM constructs alone, 16%. HBM constructs accounted for 7% additional variance in compliance beyond all other predictors and thus may be a fruitful focus for interventions to increase screening rates.

Increasing condom use: Evaluation of a theory-based intervention to prevent sexually transmitted diseases in young women

A multicomponent intervention to increase condom use in sexually active young women was designed, implemented, and evaluated in a randomized experiment. Participants were 198 unmarried female college students (mean age = 18.6 years) who received a 1-session condom promotion intervention or a control (stress management) intervention. The condom promotion intervention led to increased self-reported condom use up to 6 months following intervention as well as positive changes in perceived benefits of condom use, affective attitudes toward condom use and condom users, perceived acceptance of sexuality, control over the sexual encounter, perceived self-efficacy for condom use, and intentions to use condoms. Mediational analysis illustrated the mechanisms of the condom promotion intervention effects, linking psychological constructs affected by the intervention (perceived benefits, acceptance of sexuality, control over the sexual encounter, attitudes toward condoms, and self-efficacy for condom use) to condom use intentions.

The health belief model and adolescents with insulin-dependent diabetes mellitus.

We tested the predictive utility of the health belief model (HBM) for adherence with a complex, ongoing medical regimen in the context of a chronically ill youthful population (56 adolescent outpatients with insulin-dependent diabetes mellitus; mean age = 14 years). A three-construct model of health beliefs was tested: Threat (perceived susceptibility combined with severity), Benefits-Costs, and Cues to seek treatment. Multiple indicators of compliance were used, and metabolic control was measured by glycosylated hemoglobin. The Benefits-Costs and Cues constructs were related to compliance in the theoretically expected positive direction. Threat interacted with Benefits-Costs in the prediction of compliance and with Cues in the prediction of metabolic control. The greatest compliance was achieved with low perceived Threat and high perceived Benefits-Costs. Poor metabolic control was associated with high Threat and Cues. As age increased, adherence to the exercise, injection, and frequency components of the regimen decreased.

Young women's condom use: the influence of acceptance of sexuality, control over the sexual encounter, and perceived susceptibility to common STDs.

A comprehensive model of the determinants of condom use among young women was developed, tested, and replicated, with longitudinal follow-up to assess predictive utility of the model for condom use over time. Participants in Study 1 and Study 2 were 198 female undergraduates (mean age, 18.6 years) and 238 female undergraduates (mean age, 19.1 years), respectively. Acceptance of sexuality and control over the sexual encounter were related to a multidimensional measure of condom use self-efficacy, which predicted condom use intentions. Perceived susceptibility to STDs was both directly related to intentions and indirectly related through perceived benefits and attitudes about condom use. Intentions predicted subsequent reports of condom use. The model suggests foci for condom use interventions for young women.

The Impact of Internalized Homophobia on HIV Preventive Interventions

A growing body of research implicates internalized homophobia—the internalization of societys antihomosexual sentiments by gay and lesbian people—as a factor contributing to HIV-related sexual risk behavior in gay and bisexual men. Although accumulating evidence links internalized homophobia and sexual risk behavior, no study has explored the impact of internalized homophobia on efforts to prevent these behaviors. This paper examines the effect of internalized homophobia on gay and bisexual mens awareness of, participation in, and perceptions of programs offered by a community-based HIV prevention organization. In Study 1, 595 gay and bisexual men reported their levels of awareness of and participation in HIV prevention programming offered by one community organization. Internalized homophobia was negatively related to mens awareness of the services offered by the organization. However, among the men who were aware of at least one service, internalized homophobia did not further predict service utilization. Study 2 examined 89 gay and bisexual men who participated for a single session in a group-structured, community-based HIV preventive intervention. Pre- to immediate postintervention change in perceptions of condom use self-efficacy was inversely related to internalized homophobia. Internalized homophobia was also a significant negative predictor of the extent to which participants felt similar to and related well with other members of the group. Together, these findings suggest that internalized homophobia may pose multiple barriers to community-based HIV prevention efforts.

Evaluation of a multicomponent appearance-based sun-protective intervention for young women: Uncovering the mechanisms of program efficacy.

An appearance-based sun-protection intervention program was developed, implemented, and evaluated in a sample of 211 Caucasian women (ages 18-25) randomly assigned to the sun-protection program or to a stress management (control) program. The sun-protection program incorporated a novel construct of image norms of aspirational peers (i.e., female media figures, fashion models) approving paleness. The authors targeted these image norms as well as the advantages of tanning, health beliefs about photoaging and skin cancer, and self-efficacy for sun protection. The intervention produced significant differences across conditions favoring sun protection on all constructs but severity of skin cancer and barriers to sun protection. At follow-up, treatment participants exceeded controls both in intention to sun protect and sun-protective behavior and reported lower intention to sunbathe and fewer hours of sunbathing. A mediational model of intervention outcomes revealed distinct mediators for sun protection versus sunbathing.