The trend of intelligence in certain districts of England

An estimate of the change in intelligence in ten English education authorities during the past 10 years has been made by comparing the scores of complete year groups of 11-year-old children in 1947 with scores made by similar groups in the same test on an earlier occasion. The first test was taken by 31,728 children and the second by 28,505 children, boys and girls in approximately equal numbers.

For boys and girls together there was a fall of 0.0034 point of intelligence quotient per year, which was far from significant. In seven districts where we had separate scores for boys and girls on both occasions there was a significant fall in intelligence quotient of 0.0921 point per year amongst boys and a significant rise of 0.0921 point per year amongst girls.

The adventitious influences which might invalidate a comparison of the two sets of scores have been considered; they probably tend to depress the score at the second test.

A study of sex differences in attainment tests at 11 years and in intelligence tests at 13 years and later suggests that the scores of the boys in 1947 are underestimates of their ability, and that a truer measure of the trend of intelligence amongst the population is represented by the change in the girls' scores.

By assuming a certain parallelism between the present survey and that of the Scottish children, the rise in intelligence quotient of the latter is estimated at 0.0543 point per year.

A significant increase in the dispersion of intelligence test score of both boys and girls during the past 10 years has been recorded.     

Pre‐procreative ages in population stability and cyclicity

Age‐specific models of population renewal (with and without feedback) which imply convergence to a stable state for some levels of fertility or feedback may imply the presence of long‐term cycling around a constant or exponentially changing equilibrium for other levels of fertility or feedback. The switch from one regime to the other is a “bifurcation.”; The conditions for bifurcation involve the roots of an analogue of Lotka's Equation.

Typically bifurcation is induced by raising the strength of feedback or the level of fertility. It has been known since the early 1980s, however, that this is sometimes impossible. It is sometimes impossible even with the linear renewal equation itself and with the most basic of non‐linear models, Lee's cohort feedback model.

Here it is proved that this typical route to bifurcation does not fail for these basic models in the presence of a condition which always holds for realistic applications with higher organisms: the existence of a span of ages before the onset of fertility.

Specifically, a strictly positive lower bound on ages of procreation is proved to be sufficient to guarantee the existence of a rescaling of Lotka's Equation for which the real part of some complex root vanishes. This result holds for absolutely Lebesgue‐integrable (signed) net maternity functions on the positive real line and for absolutely summable (signed) net maternities on the positive integers.

It follows that Coale's rescaling device for the analysis of approach to stability in stable population theory can be implemented for all realistic human net maternity schedules. It also follows that the many special cases of the cohort feedback model throughout population biology will all generate persistent cycling instead of stability if feedback is sufficiently strong.     

The estimation of fertility rates from ratios of total to first births

In a previous paper a formula was derived from which the total fertility rate of a group of women could be estimated from the average number of live births to women in the reproductive period. In the present paper the argument is carried further and a method is given by which the total fertility rate may be estimated from the average number of children born to fertile women during the reproductive period. The method given in this paper may, under certain circumstances, have considerable advantages over the previous method suggested.     

On the α-risks for shewhart control charts

The performance of the usual Shewhart control charts for monitoring process means and variation can be greatly affected by nonnormal data or subgroups that are correlated. Define the α_k-risk for a Shewhart chart to be the probability that at least one “out-of-control” subgroup occurs in k subgroups when the control limits are calculated from the k subgroups. Simulation results show that the α_k-risks can be quite large even for a process with normally distributed, independent subgroups. When the data are nonnormal, it is shown that the α_k-risk increases dramatically. A method is also developed for simulating an “in-control” process with correlated subgroups from an autoregressive model. Simulations with this model indicate marked changes in the α_k-risks for the Shewhart charts utilizing this type of correlated process data. Therefore, in practice a process should be investigated thoroughly regarding whether or not it is generating normal, independent data before out-of-control points on the control charts are interpreted to be due to some real assignable cause.     

Changes in sex practices and beliefs of male college students: Over 30 years∗

Abstract

Replication of an earlier survey, using the same questionnaire in the same college course, reveals an increase in proportion of male students with premarital heterosexual experience, from 45 per cent in 1943–44 to 61.8 per cent in 1967–68 and 74.9 per cent in 1969–73. While the mean number of episodes is also greatly increased, the tendency is toward reducing the number of partners. Since the proportion condoning premarital intercourse has risen to over 90 per cent, still further increments in activity may be anticipated. The number reporting homosexual behavior (most often limited to the pre‐ and early‐adolescent years) has declined from 27 per cent to 13.7 per cent, but the amount of activity during the college years has increased. Students having experienced a particular sexual activity impute that activity to a higher proportion of the general population than do the inexperienced.     

Ridge Regression: Degrees of Freedom in the Analysis of Variance

It appears to be common practice with ridge regression to obtain a decomposition of the total sum of squares, and assign degrees of freedom, according to established least squares theory. This discussion notes the obvious fallacies of such an approach, and introduces a decomposition based on orthogonality, and degrees of freedom based on expected mean squares, for non-stochastic k.     

College women and the occurrence of unwanted sexual advances in public drinking settings

Using existing data from the 1999 Harvard School of Public Health College Alcohol Study, this study analyzes the social predictors of unwanted sexual advances experienced by college women and where this type of victimization occurs. Routine activities theory informed the analysis. While attendance and increased alcohol consumption at bars have a significant effect on experiences of unwanted sexual advances, attendance at parties, attendance at drink promotions, and participation in drinking games does not. Furthermore, while less satisfaction with education, having more sexual partners and friends that binge drink, and having more alcohol-related problems increase the likelihood of experiencing unwanted sexual advances, so does drinking less in general, having higher educated parents, and having a higher grade point average. These findings show that the predictors of unwanted sexual advances may differ somewhat from those that predict more serious forms of sexual victimization. Implications for future research and policy are discussed.     

The effect of non-normality on estimating the variance of the combined ratio estimate in complex surveys

The performance of the balanced half-sample, jackknife and linearization methods for estimating the variance of the combined ratio estimate is studied by means of a computer simulation using artificially generated non-normally distributed populations.

The results of this investigation demonstrate that the variance estimates for the combined ratio estimate may be highly biased and unstable when the underlying distributions are non-normal. This is particularly true when the number of observations available from each stratum is small. The jack-     

Reciprocal Family,Friendship and Church Support Networks of African Americans: Findings from the National Survey of American Life

This study examined reciprocal support networks involving extended family, friends and church members among African Americans. Our analysis examined specific patterns of reciprocal support (i.e., received only, gave only, both gave and received, neither gave or received), as well as network characteristics (i.e., contact and subjective closeness) as correlates of reciprocal support. The analysis is based on the African American subsample of the National Survey of American Life. Overall, our findings indicate that African Americans are very involved in reciprocal support networks with their extended family, friends and church members. Respondents were most extensively involved in reciprocal supports with extended family members, followed closely by friends and church networks. Network characteristics (i.e., contact and subjective closeness) were significantly and consistently associated with involvement with reciprocal support exchanges for all three networks. These and other findings are discussed in detail. This study complements previous work on the complementary roles of family, friend and congregational support networks, as well as studies of racial differences in informal support networks.