在网页中样本量计算第一个栏目，RCT/队列研究+分类研究栏目，描述了一个新英格兰2015年一篇文章举例，问题如下。 本人使用PASS15.0计算，然后按照文中缩写步骤，得出的结果为如下，样本量和文中不一致，有点出入。 PASS 15.0.5    10/1/2018 12:47:41 PM      1 Tests for Two Proportions Numeric Results for Testing Two Proportions using the Z-Test with Unpooled Variance H0: P1 - P2 = 0.   H1: P1 - P2 = D1 ≠ 0. Target    Actual                Target    Actual            Diff         Power    Power*    N1    N2    N    R    R    P1    P2    D1    Alpha     0.90    0.90017    2173    1087    3260    0.50    0.50    0.1000    0.1400    -0.0400    0.0500     * Power was computed using the normal approximation method. References Chow, S.C., Shao, J., and Wang, H. 2008. Sample Size Calculations in Clinical Research, Second Edition.    Chapman & Hall/CRC. Boca Raton, Florida. D'Agostino, R.B., Chase, W., and Belanger, A. 1988. 'The Appropriateness of Some Common Procedures for Testing    the Equality of Two Independent Binomial Populations', The American Statistician, August 1988, Volume 42    Number 3, pages 198-202. Fleiss, J. L., Levin, B., and Paik, M.C. 2003. Statistical Methods for Rates and Proportions. Third Edition.    John Wiley & Sons. New York. Lachin, John M. 2000. Biostatistical Methods. John Wiley & Sons. New York. Machin, D., Campbell, M., Fayers, P., and Pinol, A. 1997. Sample Size Tables for Clinical Studies, 2nd    Edition. Blackwell Science. Malden, Mass. Ryan, Thomas P. 2013. Sample Size Determination and Power. John Wiley & Sons. Hoboken, New Jersey. Report Definitions Target Power is the desired power value (or values) entered in the procedure. Power is the probability of    rejecting a false null hypothesis. Actual Power is the power obtained in this scenario. Because N1 and N2 are discrete, this value is often    (slightly) larger than the target power. N1 and N2 are the number of items sampled from each population. N is the total sample size, N1 + N2. Target R is the desired ratio (or ratios) of R entered in the procedure. R is the ratio of N2 to N1, so that    N2 = R × N1. Actual R is the value for R obtained in this scenario. Because N1 and N2 are discrete, this value is sometimes    slightly different than the target R. P1 is the proportion for Group 1 at which power and sample size calculations are made. This is the treatment    or experimental group. P2 is the proportion for Group 2. This is the standard, reference, or control group. D1 is the difference P1 - P2 assumed for power and sample size calculations. Alpha is the probability of rejecting a true null hypothesis. Summary Statements Group sample sizes of 2173 in group 1 and 1087 in group 2 achieve 90.017% power to detect a difference between the group proportions of -0.0400. The proportion in group 1 (the treatment group) is assumed to be 0.1400 under the null hypothesis and 0.1000 under the alternative hypothesis. The proportion in group 2 (the control group) is 0.1400. The test statistic used is the two-sided Z-Test with unpooled variance. The significance level of the test is 0.0500. PASS 15.0.5    10/1/2018 12:47:41 PM      2 Tests for Two Proportions Dropout-Inflated Sample Size         Dropout-Inflated    Expected         Enrollment    Number of     ──── Sample Size ────    ──── Sample Size ────    ───── Dropouts ───── Dropout Rate    N1    N2    N    N1'    N2'    N'    D1    D2    D 20%    2173    1087    3260    2717    1359    4076    544    272    816 Definitions Dropout Rate (DR) is the percentage of subjects (or items) that are expected to be lost at random during the    course of the study and for whom no response data will be collected (i.e. will be treated as "missing"). N1, N2, and N are the evaluable sample sizes at which power is computed. If N1 and N2 subjects are evaluated    out of the N1' and N2' subjects that are enrolled in the study, the design will achieve the stated power. N1', N2', and N' are the number of subjects that should be enrolled in the study in order to end up with N1,    N2, and N evaluable subjects, based on the assumed dropout rate. After solving for N1 and N2, N1' and N2'    are calculated by inflating N1 and N2 using the formulas N1' = N1 / (1 - DR) and N2' = N2 / (1 - DR), with    N1' and N2' always rounded up. (See Julious, S.A. (2010) pages 52-53, or Chow, S.C., Shao, J., and Wang, H.    (2008) pages 39-40.) D1, D2, and D are the expected number of dropouts. D1 = N1' - N1, D2 = N2' - N2, and D = D1 + D2. Procedure Input Settings Autosaved Template File C:\Users\lenovo\Documents\PASS 15\Procedure Templates\Autosave\Tests for Two Proportions - Autosaved 2018_10_1-12_47_42.t359 Design Tab Solve For:    Sample Size Power Calculation Method:    Normal Approximation Alternative Hypothesis:    Two-Sided Test Type:    Z-Test (Unpooled) Power:    0.90 Alpha:    0.05 Group Allocation:    Enter R = N2/N1, solve for N1 and N2 R:    0.5 Input Type:    Proportions P1 (Group 1 Proportion|H1):    0.1 P2 (Group 2 Proportion):    0.14