An experiment was performed to test the influence of two factors on assortative mating in the Jewel wasp (Nasonia vitripennis): (1) inherited eye-color genotype, and (2) conditioned foraging phenotype. To determine the female choice of sires, genetically marked wasps were used of two recessive mutant eye-color genotypes: white or red. Each female (of independently crossed eye-color and juvenile host) was given a choice of two males, one of each eye-color, counterbalanced for juvenile host: blowfly (Sarcophaga bullata) or housefly (Musca domestica) pupae. Blowfly-reared females produced more total offspring, indicating higher fertility. Red-eyed females produced more offspring sired by red-eyed males, indicating assortative mating by eye color. Blowfly-reared females, however, did not produce more offspring sired by blowfly-reared males, indicating no assortative mating by juvenile host.

This paper discusses the conceptual and mathematical relationships between three statistical models: 1) traditional, or “Simultaneous”, Canonical Analysis, 2) hierarchical, or “Sequential”, Canonical Analysis, and 3) Structural Equations Modeling, or confirmatory path analysis. The advantages of Sequential over Simultaneous Canonical Analysis are reviewed. The relationships between Sequential Canonical Analysis and Path Analysis are explored. The need for a legitimate exploratory form of path analysis, analogous to existing exploratory forms of both multiple regression and factor analysis, is discussed. A logical extension of Sequential Canonical Analysis is proposed as adequately serving the function of an exploratory path analysis. Empirical data from psychological research is used to illustrate and qualitatively compare and contrast the results of these three approaches.

The Trivers-Willard model (1973) predicts differential parental investment in children by sex and income; wealthier families will invest more in boys, while poorer families will invest more in girls. We investigated the TW Hypothesis in a sample of 103 six month old Tucson babies and their mothers. Hierarchical multiple regression equations were used entering baby's age, baby's sex, mother's age, male paternal commitment, a dichotomous poverty measure, per capita income, and four interaction terms, baby's sex by 1 ) mother's age 2) mother's education, 3) male paternal commitment, 4) poverty, and 5) per capita income. We included three dependent variables in successive regression equations; mother's attitudes towards ideal baby size for boy versus girl babies, weeks breast fed and the baby's weight at six months. These variables measure attitude, behavior, and physical outcomes. Poverty was a significant predictor of differential preference in ideal body size for boys versus girls; poor mothers preferred bigger baby girls. There was no evidence of differential preference in breast feeding. Education was also a significant predictor; but in the opposite direction than predicted by the TWH. Mothers with higher levels of education had heavier baby girls. Within Hispanics only, poverty was a significant predictor of sex-biased weight; poor mothers had heavier baby girls. This effect was not seen in Caucasians. These results provide mixed evidence for the Trivers-Willard model in a resource rich environment for humans.

Survivorship of children is dependent upon numerous variables, including the role that preferential treatment may play in biasing the birth and survival of sons and daughters across cultures. This study draws upon an evolutionary approach by examining a theory referred to as the “Trivers-Willard hypothesis” concerning condition-dependent sex allocation and differential parental investment. Previous research on humans concerning this hypothesis tends to be restricted to one cultural group and thereby limited in sample size. For this study, nationally representative household survey data collected by the Demographic and Health Surveys (DHS ) program across 35 countries was used to test biological, resource-oriented, and behavioral aspects affecting maternal condition, sex allocation, and parental investment in humans. The units of analysis for this study were the mothers and their lastborn child (N = 128,039 woman-child pairs). A series of hierarchical regressions were executed to empirically investigate the TW hypothesis in humans. Scales were developed for maternal socioeconomic resources (MSR), maternal biological condition (MBC), prenatal care for the lastborn child (PCL), and health-seeking for the lastborn child (HSL). MSR was measured by relative household economic status, woman's and partner's education, and residence in an urban/rural setting. MBC was defined by body mass index, pregnancy status and duration, and breast-feeding status. PCL was an index for type of prenatal care received, number of prenatal visits, and assistance during delivery of the lastborn child. Lastly, HSL measured indicators of treatment for diarrhea and immunizations received by the lastborn child. Across the 35 countries, the analyses did not support the Trivers-Willard hypothesis. However, there is evidence of regional and country level differences.

Previous HIV/AIDS assessments in Kenya have focused on the sexual risk behaviors of the general population and the HIV serostatus of women of childbearing age. No data are available for Kenyan university students. Baseline surveillance data were obtained from a representative sample of 1917 university students at Moi University in Eldoret, Kenya. Both qualitative (focus group discussions) and quantitative (self-administered questionnaire) data were collected. Students were asked about their HIV knowledge, perceptions, and sexual risk behaviors. Seventy-one % of males and 47.6% of females reported having had sex. Only 49% of university students reported any HIV/AIDS education. Of those who reported having ever had sex, 76% reported ever using a condom: only 18% of males and 14% of females reported using a condom every time they had sex in the last month. Eighty-nine% of students reported thinking they were at risk for HIV infection, but only 28% of subjects had been tested for HIV. Qualitative data suggest the issue of HIV testing remains very controversial among students, in large part because of societal stigma. The results of this study emphasize the vulnerability of university students to HIV infection. Most university students have not had access to accurate HIV/AIDS information. Sexual activity on campus is high and many students consider themselves at risk. Conversely, consistent condom use and rates of voluntary counseling and testing are low.

A previous study using frequentist analytic methods on a single cohort showed no difference in forty-one patients under chiropractic management for mild or early stage scoliosis. The grantor requested a re-analysis. Plain film radiographs of 41 children and adolescents were re-measured by Risser-Ferguson and Cobb methods. Three magnitudes and three types of change were constructed to cover various notions of scoliosis change: magnitudes of 1°, 3°, or 5°, and types that alternatively included or omitted no change as a possible successful outcome (arrested progression). Improvement was assessed from using three filters across three definitions of progression: 1) curve improved or stable, 2) improved only, and 3) those that either improved or progressed. Data were then analyzed by evidential support methods and Bayesian analyses at each filter and type of progression to establish whether improvement was likely attributable to treatment or spine characteristics.

Intra-class correlation for intra-examiner stability was 0.73 by Cobb method. Reliability between the new and the previous examiner was 0.59 for pre- and 0.69 for post-treatment Cobb angles. Reliability increased dramatically when end vertebrae were specified. Ratio of number improved to those progressed to was at least 2:1 for all three levels of filter: 1°, 3°, and 5°. Number of treatments or duration of care were not associated with improvement. However, the number of vertebral segments below the scoliosis curve apex — a measure of curve compression ûand bone age accounted for 49% of adjusted R² in Cobb angle changes. Initial Cobb angle as a clinical predictor was not supported. One treating chiropractor experienced a greater rate of improvement at the highest level of change (5°) in his patients. Results here could not be attributed to management, but could be from a type of scoliosis resolving spontaneously, or a subgroup of scoliosis cases that responded to chiropractic management or manipulation.