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Cluster Unit Randomized Trials

5. Pair-Matching

Table 2 lists estimated values of ρM (updated from Donner and Klar, 2000, Table 3.2) for a variety of recently published matched-pair trials. The values reported here clearly indicate that the effectiveness of matching can vary greatly from study to study. For example the HIV prevention trial reported by Grosskurth et al., 1995 generated an unusually high matching correlation of 0.94, while two other community-based trials actually generated negative estimates of ρM. It is also interesting to note that the estimated value of ρM for the COMMIT trial is given by 0.21, barely meeting the criterion given by Martin et al., 1993.

Table 2

Matching Correlations

SourceUnit of Randomization Number of Pairs Outcome Variable Matching Correlation
Stanton & Clemens (1987) Cluster of Families
25Childhood Diarhea Rate 0.49
Kidane & Morrow (2002) Cluster of Villages 12Childhood of Morality -0.39
Thompson et al., (1997)Physician Practice 13Levels of Coronary Risk Factors 0.13
Ray et al., (1997)Nursing Home7Rate of Recurrent Falling 0.63
Peterson et al.(2002) School district 20Prevalence of Smoking0.34
Haggerty et al., (1994) Community 9Childhood Diarrhea Rate -0.32
Grosskurth et al., (1995) Community 6HIV Rate 0.94
The COMMIT Research Group (1995) Community 11Smoking Quit Rate 0.21
Donner A., Klar N. (2000). Design and analysis of cluster randomization trials in health research. New York: Oxford University Press.
Kidane G., Morrow R.H. (2000). Teaching mothers to provide home treatment of malaria inTigray , Ethiopia : A randomised trial. Lancet, 356: 550-555.
Thompson S.G., Pyke S.D.M., Hardy R.J. (1997). The design and analysis of paired cluster randomized trials: An application of meta-analysis techniques. Statistics in Medicine, 16: 2063-2980.
Ray W.A., Taylor J.A., Meador K.G., Thapa P.B., Brown A.K., Kajihara H.K., Davis C., Gideon P., Griffin M.R. (1997). A randomized trial of a consultation service to reduce falls in nursing homes. Journal of the American Medical Association, 278: 557-562.
Peterson A.V. Jr., Kealey K.A., Mann S.L., Marek P.M., Sarason I.G. (2002). Hutchinson smoking Prevention Project: Long-term randomized trial in school-based tobacco use prevention-results on smoking. Journal of the National Cancer Institute, 92:1979-1991.
Haggerty P.A., Muladi K., Kirkwood B.R., Ashworth A., Manunebo, M. (1994). Community-based hygiene education to reduce diarrhoeal disease in rural Zaire : Impact of the intervention on diarrhoeal morbidity. International Journal of Epidemiology, 23:1050-1059.