Sample Selectivity and Generalizability of the Results of the Berlin Aging Study

Abstract

In epidemiological investigations, one common but rarely analyzed threat to generalizability is sample selectivity or nonrandom sample attrition. In this chapter, we describe our approach to the study of selectivity and provide indepth analyses of the magnitude of sample selectivify in the Berlin Aging Study. Of all individuals eligible for participation (the verified parent sample, N = 1,908), 27Vo reached the highest level of participation (the Intensive Protocol, N = 516). \4/ith respect to levels of performance, projection of selectivity observed on lower levels ofparticipation onto Intensive Protocol constructs indicates that the Intensive Protocol sample was, indeed, positively selected on medical, social, and psychological dimensions. However, the magnitude of observed selectivity effects did not exceed 0.5 standard deviations for any construct. In addition, variances and covariance relations observed in the Intensive Protocol sample were not markediy different from those found at lower levels of participation. We conclude that the degree of selectivity in BASE fell within the usual range and did not result in a decrease of sample heterogeneity. Given the magnitude of sample attrition and the high mean age of the sample, this is a satisfactory result.

Selectivity Processes in and Weights for the Berlin Aging Study II (Base-II)

“…This finding is in line with that of Lindenberger et al (1999), who analysed attrition in the BASE-I study, a probability sample of the elderly aged 74 and older in West Berlin. No health-related selectivity was found in the BASE-I study, except in regard to BMI.…”

“…But even surveys based on a probability sample face problems of selectivity due to selective unwillingness of randomly selected potential subjects (respondents) to participate in SOEP Survey Papers 229 the survey. Lindenberger et al (1999) and also Schaie et al (1973) emphasise that initial sample selectivity has to be distinguished from selectivity due to attrition.…”

Daily Activities and Survival at Older Ages

“…The study design consists of a hierarchical sequence of four levels of participation, with increasing numbers of variables but decreasing numbers of participants at each consecutive level: the verified parent sample (n = 1,908); the short-contact sample (n = 1,264); the intake assessment sample (n = 928); and the intensive protocol sample (n = 516), used in the present study, with its 14 sessions of multidisciplinary assessment. Extensive selectivity analyses (Lindenberger et al, 1999) showed the intensive protocol sample to be a somewhat positive selection of the parent sample. The magnitude of the selectivity effects was largest for general intelligence, but it did not exceed half a standard deviation for any of the analyzed domains of functioning.…”

Social Participation Attenuates Decline in Perceptual Speed in Old and Very Old Age.

“…Hierarchically nested selectivity analyses comparing the 516 individuals who were willing and able to complete the comprehensive t1 assessment with the total parent sample revealed that the 516 individuals were positively selected on a broad range of variables covering demographic, sensory/sensorimotor, life history, and intellectual domains (for details, see Lindenberger et al, 1999). However, with the exception of dementia prevalence, effect size estimates were well below 0.5 standard deviation.…”