Improving consumption measurement and other survey data through CAPI: Evidence from a randomized experiment

This paper reports on a randomized survey experiment among 1840 households, designed to compare pen-and-paper interviewing (PAPI) to computer-assisted personal interviewing (CAM). We find that PAPI data contain a large number of errors, which can be avoided in CAPI. Error counts are not randomly distributed across the sample, but are correlated with household characteristics, potentially introducing sample bias if dubious observations need to be dropped. We demonstrate a tendency for the spread of total measured consumption to be higher on paper compared to CAPI, translating into significantly higher measured inequality. Investigating further the nature of PAPI's measurement error for consumption, we fail to reject the hypothesis that it is classical: it attenuates the coefficient on consumption when used as explanatory variable and we find no evidence of bias when consumption is used as dependent variable. Finally, CAPI and PAPI are compared in terms of interview length, costs and respondents' perceptions. (C) 2011 Elsevier B.V. All rights reserved,