chapter6randomerror-資料下載頁
2025-07-15 18:06本頁面
【正文】 age of using variance is that variances are additive. ? ? ? ?s ?????? ?? ?x xNdNiiNiiN1 11 12 2 Relative Standard Deviation (RSD) and Coefficient of Variation (CV) We calculate the relative standard deviation by dividing the standard deviation by the mean of the set of data. It is often expressed in parts per thousand (ppt) or in percent by multiplying this ratio by 1000 ppt or by 100%. RSD = s/x x 1000 ppt The relative standard deviation multiplied by 100% is called the coefficient of variation (CV). CV = s/x x 100% Relative standard deviations often give a clearer picture of data quality than do absolute standard deviations. Spread or Range (w): The spread, or range, is another term that is sometimes used to describe the precision of a set of replicate results. It is the difference between the largest value in the set and the smallest. Reporting Computed Data A numerical result is worthless unless the user knows something about its accuracy and/or precision. It is always essential to indicate best estimate of the reliability of data. One of the best ways of indicating reliability is to give a confidence interval at the 90% or 95% confidence level. Another method is to report the absolute standard deviation or the coefficient of variation of the data. It is a good idea to indicate the number of data points that were used to obtain the standard deviation so that the user has some idea of the probable reliability of s. Less satisfactory but more mon indicator of the quality of data is the significant figure convention.
研究報告相關(guān)推薦
鄂ICP備17016276號-1