Abstract
The analysis of data obtained from a clinical trial represents the outcome of the planning and implementation already described. Primary and secondary questions addressed by the clinical trial can be tested and new hypotheses generated. Data analysis is sometimes viewed as simple and straightforward, requiring little time, effort, or expense. However, careful analysis usually requires a major investment in all three. It must be done with as much care and concern as any of the design or data-gathering aspects. Furthermore, inappropriate statistical analyses can introduce bias, result in misleading conclusions, and impair the credibility of the trial.
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Appendix
Appendix
Mantel–Haenszel Statistic
Suppose an investigator is comparing response rates and divides the data into a number of strata using baseline characteristics. For each stratum i, a 2 × 2 table is constructed.
2 × 2 Table for ith Stratum | |||
Response | |||
Yes | No | ||
Intervention | a i | b i | a i + b i |
Control | c i | d i | c i + d i |
Total | a i + c i | b i + d i | n i |
The entries a i , b i , c i , and d i represent the counts in the four cells and n i is the number of participants in the ith stratum. The marginals represent totals in the various categories. The value (a i + c i )/n i represents the overall response rate for the ith stratum. Within the ith stratum, the rates a i /(a i + b i ) with c i /(c i +d i ) are compared. The standard chi-square test for 2 × 2 tables could be used to compare group differences in this stratum. However, the investigator is interested in “averaging” the comparison over all the strata. The method for combining several 2 × 2 tables over all tables or strata was described by Cochran [157] and Mantel and Haenszel [158]. The summary statistic, denoted MH, is given by:
The MH statistic has a chi-square distribution with one degree of freedom. The square root of MH has a normal distribution. Tables for this distribution are available in standard statistical textbooks. Any value for MH greater than 3.84 is significant at the 0.05 level, and any value greater than 6.63 is significant at the 0.01 level. This method is particularly appropriate for covariates that are discrete or continuous covariates that have been classified into intervals.
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Friedman, L.M., Furberg, C.D., DeMets, D.L. (2010). Issues in Data Analysis. In: Fundamentals of Clinical Trials. Springer, New York, NY. https://doi.org/10.1007/978-1-4419-1586-3_17
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DOI: https://doi.org/10.1007/978-1-4419-1586-3_17
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