임상시험에서 중도탈락을 고려한 표본크기의 결정

Sample Size Calculations with Dropouts in Clinical Trials

The sample size in a clinical trial is determined by the hypothesis, the varianceof observations, the eect size, the power and the signicance level. Dropouts inclinical trials are inevitable, so we need to consider dropouts on the determinationof sample size. It is common that some proportion corresponding to the expecteddropout rate would be added to the sample size calculated from a mathematicalequation. This paper proposes new equations for calculating sample size dealingwith dropouts. Since we observe data longitudinally in most clinical trials, we canuse a last observation to impute for missing one in the intention to treat(ITT) trials, and this technique is called last observation carried forward(LOCF). But LOCF might make deviations on the assumed variance and eect size, so that we could not guarantee the power of test with the sample size obtained from the existing equation. This study suggests the formulas for sample size involving information about dropouts and shows the properties of the proposed method in testing equality of means.

The sample size in a clinical trial is determined by the hypothesis, the varianceof observations, the eect size, the power and the signicance level. Dropouts inclinical trials are inevitable, so we need to consider dropouts on the determinationof sample size. It is common that some proportion corresponding to the expecteddropout rate would be added to the sample size calculated from a mathematicalequation. This paper proposes new equations for calculating sample size dealingwith dropouts. Since we observe data longitudinally in most clinical trials, we canuse a last observation to impute for missing one in the intention to treat(ITT) trials, and this technique is called last observation carried forward(LOCF). But LOCF might make deviations on the assumed variance and eect size, so that we could not guarantee the power of test with the sample size obtained from the existing equation. This study suggests the formulas for sample size involving information about dropouts and shows the properties of the proposed method in testing equality of means.