Sampling design effects: Do they affect the analyses of data from the national survey of families and households?

Most large national surveys, such as the National Survey of Families and Households (NSFH), involve clustered and stratified samples. These complex sample designs have consequences for data analysis techniques. Standard errors calculated using procedures that do not adjust for design effects often are too small and lead to incorrect inferences. We discuss design effects and estimate them for a set of variables selected from the 1988 NSFH. Included are examples of descriptive estimates and regression results with household income and marital happiness as dependent variables. Statistical software that adjusts standard errors in complex designs is discussed, as are issues related to weighting and the analysis of subsamples.