How non-normality affects the quadratic discriminant function

The quadratic discriminant function is commonly used for the two group classification problem when the covariance matrices in the two populations are substantially unequal. This procedure is optimal when both populations are multivariate normal with known means and covariance matrices. This study examined the robustness of the QDF to non-normality. Sampling experiments were conducted to estimate expected actual error rates for the QDF when sampling from a variety of non-normal distributions. Results indicated that the QDF was robust to non-normality except when the distributions were highly skewed, in which case relatively large deviations from optimal were observed. In all cases studied the average probabilities of misclassification were relatively stable while the individual population error rates exhibited considerable variability.     

Interval estimation for log-linear models with one variable subject to non-ignorable non-response

Summary.  Log-linear models for multiway contingency tables where one variable is subject to non-ignorable non-response will often yield boundary solutions, with the probability of non-respondents being classified in some cells of the table estimated as 0. The paper considers the effect of this non-standard behaviour on two methods of interval estimation based on the distribution of the maximum likelihood estimator. The first method relies on the estimator being approximately normally distributed with variance equal to the inverse of the information matrix. It is shown that the information matrix is singular for boundary solutions, but intervals can be calculated after a simple transformation. For the second method, based on the bootstrap, asymptotic results suggest that the coverage properties may be poor for boundary solutions. Both methods are compared with profile likelihood intervals in a simulation study based on data from the British General Election Panel Study. The results of this study indicate that all three methods perform poorly for a parameter of the non-response model, whereas they all perform well for a parameter of the margin model, irrespective of whether or not there is a boundary solution.     

Researching Children: Methods and Ethics

The appropriateness and desirability of researching children have been issues of some debate. Children may be perceived as non-competent or vulnerable, and proxies have been used as children's representatives. Increasingly researchers are speaking to children directly. Why is this so and what are the methodological and ethical implications of researching children's views? In this paper the authors draw on their own experiences of researching children in the fields of child carers and the impact of the Child Support Act 1991. A number of social, political and legal trends are identified which form a background to the growing interest in children as potential and actual participants in the research process. The theoretical, methodological, ethical and practical issues involved are then identified and described, using examples from two separate studies conducted by the authors.     

Zusammenfassungen

Ohne Zusammenfassung     

The Relationship between Economic Development and Social Welfare: A New Adjusted GDP Measure of Welfare

Existing literature focuses on the issue ofpreparation of social welfare measurements onthe basis of an unadjusted Gross DomesticProduct (GDP). This paper extends this methodto incorporate cost-benefit analysis ofeconomic growth in a growing economy incalculating the adjusted GDP, termed as thecost-benefit (CB)-adjusted GDP. This approachis empirically applied to Thailand. There arestark differences between GDP per capita and CBadjusted GDP per capita rates for this period.This paper concludes that GDP can be used as anindicator of social welfare if the GDPestimates are undertaken within a cost-benefitanalysis framework.     

Remarriage in later life: older women's negotiation of power, resources and domestic labor

Using data from in-depth interviews with 24 community-dwelling women aged 52-90, this paper analyzes the remarriage experiences of older women in contrast to their first marital relationships. The women's accounts of their experiences in their first and later life marriages are examined in terms of the negotiation of power, resources, and domestic labor. While first marriages were frequently characterized by incompatibility, alcoholism, abuse, and infidelity, second marriages were viewed as the marriages the women wished they had had in the first place or as relationships that met their later life needs. The women's lived experiences are discussed in terms of the changing cultural norms pertaining to gender roles, marriage, and divorce.     

A monte carlo investigation of a statistic for a bivariate missing data problem

Testing the equal means hypothesis of a bivariate normal distribution with homoscedastic varlates when the data are incomplete is considered. If the correlational parameter, ρ, is known, the well-known theory of the general linear model is easily employed to construct the likelihood ratio test for the two sided alternative. A statistic, T, for the case of ρ unknown is proposed by direct analogy to the likelihood ratio statistic when ρ is known. The null and nonnull distribution of T is investigated by Monte Carlo techniques. It is concluded that T may be compared to the conventional t distribution for testing the null hypothesis and that this procedure results in a substantial increase in power-efficiency over the procedure based on the paired t test which ignores the incomplete data. A Monte Carlo comparison to two statistics proposed by Lin and Stivers (1974) suggests that the test based on T is more conservative than either of their statistics.     

Consideration of the Aerosol Transmission for COVID-19 and Public Health

This article analyzes the available evidence to address airborne, aerosol transmission of the SARS-CoV-2. We review and present three lines of evidence: case reports of transmission for asymptomatic individuals in association with studies that show that normal breathing and talking produce predominantly small droplets of the size that are subject to aerosol transport; limited empirical data that have recorded aerosolized SARS-CoV-2 particles that remain suspended in the air for hours and are subject to transport over distances including outside of rooms and intrabuilding, and the broader literature that further supports the importance of aerosol transmission of infectious diseases. The weight of the available evidence warrants immediate attention to address the significance of aerosols and implications for public health protection.