Reference no: EM133757883

Question

Identify 3 controls (in procedures and data collection methods) that strengthen internal validity specific to this study and tell why each control strengthens the internal validity. METHODS We conducted a cluster RCT16 in 14 clinical sites, including 4 community health centers and 10 hospitals in New York City that serve predominantly low-resource women. We calculated the sample size using Optimal Design for Multilevel and Longitudinal Research, version 0.23. On the basis of results from our previous study (d = 0.21- 0.39), with power at 0.80 and a set to 0.05, we needed 14 sites and 90 patients per site to detect a small or medium effect size of d = 0.25. We determined these estimates by an intraclass correlation coefficient (ICC) of 0.001. We initially selected clinical sites on the basis of a convenience sample. They could not be conducting group prenatal care, but they had to be committed to changing their practice to offer group prenatal care (including clinical leadership support) and have sufficient space. Sites were aware that they would be trained to offer group care either immediately (intervention condition) or after completion of study recruitment (delayed intervention condition). To minimize selection bias, we identified health.