Although we were gratified to achieve a 78 % retention rate in the study during 3 years, there remain significant differences in the demographic composition of nonrespondents in the intervention group compared with the UC group, and within the randomized treatment groups as well. (jamanetwork.com)
Although there was a lower response among families of minority groups (70 %) than among white families (84 %), (p <.01), t - tests and chi - square analyses indicated that minority - group respondents did not differ from minority - group nonrespondents on any birth status or sociodemographic variable (p >.05). (academic.oup.com)
Check out James O'Malley's recent publications «Optimal small - area estimation and design when nonrespondents are subsampled for followup» and «Modeling zero - modified count and semicontinuous data in health services research Part 1: background and overview and Part 2: case studies.» (dartmouth.edu)