The perils of straying from protocol: sampling bias and interviewer effects.

Fidelity to research protocol is critical. In a contingent valuation study in an informal urban settlement in Nairobi, Kenya, participants responded differently to the three trained interviewers. Interviewer effects were present during the survey pilot, then magnified at the start of the main survey after a seemingly slight adaptation of the survey sampling protocol allowed interviewers to speak with the "closest neighbor" in the event that no one was home at a selected household. This slight degree of interviewer choice led to inferred sampling bias. Multinomial logistic regression and post-estimation tests revealed that the three interviewers' samples differed significantly from one another according to six demographic characteristics. The two female interviewers were 2.8 and 7.7 times less likely to talk with respondents of low socio-economic status than the male interviewer. Systematic error renders it impossible to determine which of the survey responses might be "correct." This experience demonstrates why researchers must take care to strictly follow sampling protocols, consistently train interviewers, and monitor responses by interview to ensure similarity between interviewers' groups and produce unbiased estimates of the parameters of interest.

Community participation to refine measures of socio-economic status in urban slum settings in Kenya.

Ownership of household durable assets can be a useful proxy for determining relative socio-economic status in a community, but the assets that should be measured are not always unambiguous. Often the selection of asset variables has been ad hoc or not well explained in the literature. Although the benefits of conducting focus groups to design surveys are widely recognized, the use of focus groups to adapt community-specific asset indices has not previously been reported in Kenya. This article describes how focus group discussions can allow communities to express how residents value assets and distinguish relative wealth. Focus group discussions were conducted within the informal urban settlement of Kibera in Nairobi, Kenya. Participants identified assets that distinguish between the poorest and the least poor in their community. They considered whether they would move away from the slum if they had the opportunity, and many would not, citing reasons ranging from loyalty to the community to greater living expenses on the outside. Local perceptions of relative poverty and mobility provide insight into how quality of life in this setting can be assessed and potentially improved. Moreover, a qualitative approach can lead to the adaptation of a community asset index for use in further research.