Ratio = alternative procedure variance/current procedure variance = 45.0/25.0 = 1.8
Lower limit of confidence interval = ratio/F.05 = 1.8/2.168 = 0.83 Upper limit of confidence interval = ratio/F.95 = 1.8/0.461 = 3.90
Table 7. Example of Measures of Variance for Independent Runs (Specific to the Example in Appendix D) Procedure Alternative Current Variance (standard deviation) 45.0 (6.71) 25.0 (5.00) Sample Size 20 20 Degrees of Freedom 19 19
For this application, a 90% (two-sided) confidence interval is used when a 5% one-sided test is sought. The test is
one-sided, because only an increase in standard deviation of the alternative procedure is of concern. Some care must be exercised in using two-sided intervals in this way, as they must have the property of equal tails—most common intervals have this property. Because the one-side upper confidence limit, 3.90, is less than the allowed limit, 4.0, the study has demonstrated that the alternative procedure has acceptable precision. If the same results had been obtained from a study with a sample size of 15— as if 80% power had been chosen—the laboratory would not be able to conclude that the alternative procedure had acceptable precision (upper confidence limit of 4.47).
在这种情况下，当寻求单侧5%区间时，需要使用90%（双侧）置信区间。检验是单侧的，因为只有替代方法标准偏差的增加才是需要考虑的。此时使用双侧区间需要加以小心，因为他们必须具备等尾的特性－通常区间具备这一属性。因为单侧置信上限（3.90）小于允许限度（4.0），研究显示替代方法具有可接受的精密度。如果使用样本量15的研究获得了相同的结果，假设选择了80%效能，实验室不能做出替代方法具有可接受精密度的结论（此时置信上限为4.47）。
APPENDIX E: COMPARISON OF PROCEDURES—DETERMINING THE LARGEST ACCEPTABLE
DIFFERENCE, δ, BETWEEN TWO PROCEDURES
This Appendix describes one approach to determining the difference, δ, between two procedures
(alternative-current), a difference that, if achie