Batch sampling to improve power in a community trial. Experience from the Pawtucket Heart Health Program.
Experiments involving large social units, such as schools, work sites, or whole cities, are commonly limited in statistical power because the number of randomized units is small, leaving few degrees of freedom for residual (between-unit) error. The authors describe a method for increasing residual degrees of freedom in a community experiment without substantially increasing cost or difficulty. In brief, they propose that the experimental units should be divided into random subsamples (batches). Batch sampling can improve statistical power if the community endpoint means are stable over time or if their temporal variation is comparable in period to the batch-sampling schedule. The authors demonstrate the theoretical advantages of the batch system and illustrate its use with data from the Pawtucket Heart Health Program, in which such a design was implemented.
Feldman
H A
HA
New England Research Institutes/Pawtucket Heart Health Program, Watertown, MA 02172, USA.
McKinlay
S M
SM
Niknian
M
M
D000704:Analysis of Variance; D002318:Cardiovascular Diseases / Q000517:prevention & control; D003153:Community Health Services / Q000592:standards*; D003362:Cost-Benefit Analysis; D003627:Data Interpretation, Statistical; D006801:Humans; D015233:Models, Statistical; D015397:Program Evaluation / Q000191:economics / Q000379:methods*; D016032:Randomized Controlled Trials as Topic; D015203:Reproducibility of Results; D012237:Rhode Island; D012494:Sampling Studies; D013997:Time Factors