A Bayesian approach for improved pavement performance prediction

We present a method for predicting future pavement distresses such as longitudinal cracking. These predicted distress values are used to plan road repairs. Large inherent variability in measured cracking and an extremely small number of observations are the nature of the pavement cracking data, which calls for a parametric Bayesian approach. We model theoretical pavement distress with a sigmoidal equation with coefficients based on prior engineering knowledge. We show that a Bayesian formulation akin to Kalman filtering gives sensible predictions and provides defendable uncertainty statements for predictions. The method is demonstrated on data collected by the Texas Transportation Institute at several sites in Texas. The predictions behave in a reasonable and statistically valid manner.     

Regression calibration for logistic regression with multiple surrogates for one exposure

Methods have been developed by several authors to address the problem of bias in regression coefficients due to errors in exposure measurement. These approaches typically assume that there is one surrogate for each exposure. Occupational exposures are quite complex and are often described by characteristics of the workplace and the amount of time that one has worked in a particular area. In this setting, there are several surrogates which are used to define an individual's exposure. To analyze this type of data, regression calibration methodology is extended to adjust the estimates of exposure-response associations for the bias and additional uncertainty due to exposure measurement error from multiple surrogates. The health outcome is assumed to be binary and related to the quantitative measure of exposure by a logistic link function. The model for the conditional mean of the quantitative exposure measurement in relation to job characteristics is assumed to be linear. This approach is applied to a cross-sectional epidemiologic study of lung function in relation to metal working fluid exposure and the corresponding exposure assessment study with quantitative measurements from personal monitors. A simulation study investigates the performance of the proposed estimator for various values of the baseline prevalence of disease, exposure effect and measurement error variance. The efficiency of the proposed estimator relative to the one proposed by Carroll et al. [1995. Measurement Error in Nonlinear Models. Chapman & Hall, New York] is evaluated numerically for the motivating example. User-friendly and fully documented Splus and SAS routines implementing these methods are available (http://www.hsph.harvard.edu/faculty/spiegelman/multsurr.html).     

ADOLESCENT WORK AND BOYS' AND GIRLS' ORIENTATIONS TO THE FUTURE

This study compares adolescent boys' and girls' aspirations and plans concerning achievement, family, and other adult life spheres, and examines the effects of adolescent work experience on these future orientations. The data were obtained from 1001 students, chosen randomly from a list of enrolled ninth graders in a large Midwestern city. Girls were not found to have lower achievement orientations than boys. Examination of the interrelations of achievement and family plans suggests that boys see their future educational, work, and family roles as more closely integrated than do girls. Just as work and family roles are mutually supportive for adult men but in conflict for adult women, so too do employed adolescent boys appear to be developing traditional family orientations, while employed girls, especially those much exposed to formal work, expect less involvement in marriage and family life. The analyses indicate that paid work is traditionalizing for boys, promoting optimism about, and commitment to, numerous adult life domains; but for girls, formal work lessens interest in traditional female gender roles.     

A New STATISTIC FOR DETECTING INFLUENTIAL OBSERVATIONS IN A SCHEFFE' TYPE CALIBRATION CURVE

A statistic for identifying influential observations in calibration is given. The statistic is easy to interpret, and provides a useful measure of influence for Scheffé type calibration curves.     

The longevity of Jews in Canada, 1940–1942

A life table for the Jewish population of Canada, based upon their mortality experience during 1940–2, yielded an average length of life (expectation of life at birth) of 67–53 years for males and 69·89 years for females. These figures are greater than those for the general population of Canada by 4·58 years for males and 3·60 years for females. These margins decrease with advance in age; the expectations of life for Jews and for the total Canadian population are equal at age 25 in the case of females, and at age 35 in the case of males.

Jewish infants in Canada start life with a mortality rate, in the first year, only two-fifths of that for the general population. This advantage for Jews is observed through childhood, adolescence, and early maturity. However, the margin between the Jewish and total populations decreased with advance in age until, shortly after age 50, the Jews begin to show the higher mortality rates.

The Jewish populations of the United States and of Canada have great similarities in their social and economic structures. They also share, very largely, in their European origins, and they have come to North America during the same period. It is, therefore, a fair assumption that the longevity and mortality characteristics of the relatively small Jewish population of Canada may be indicative of what might be found for the millions of Jews in the United States, for whom such information is not available.