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.

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.