Sample Size Determination and Probability Level Estimation
摘要
In biological measurements, the sample size required to achieve a given confidence level and a given allowable error depends upon the variance of the specimen used. A simple chart to determine the sample size required for 3 probability levels (α＝0.01, 0.05, and 0.1) and 3 levels of allowable error of the mean (E＝5, 10, and 20•) was developed. The chart is easy to use, and only the calculation of the coefficient of variation is required. Two examples are demonstrated with a traditional iteration calculation and the proposed charting method. One sample is used to illustrate the estimation of probability level by the charting method. This charting method has the following advantages over the traditional iteration calculation method: 1) it is simple and easy to use; 2) no t-table is needed; 3) there is less chance of error due to calculation; 4) less time is required for calculation; and 5) it produces a more-accurate sample size estimation.