Selection Errors of Random Route Samples

Abstract

Random route samples are widely used in face-to-face surveys. Most previous studies of random route sample quality compare the data collected by random route samples with data from reliable sources, such as the German Microcensus. While these studies usually find few differences in the distributions of demographic variables, it is possible that other substantive variables of interest are biased if random route samples select households with unequal probabilities. This article takes a different approach to assessing the quality of random route samples. Since random routes are used when no complete list of respondents is available, it is assumed that all units have the same selection probability. This assumption is tested, by simulating all possible random routes within a German city and calculating the probability of selection for each household. The simulation results show that all three sets of tested random route instructions lead to strong deviations from a uniform distribution and two create systematic biases.