Nanivadekar A S, Kannappan A R
Pfizer Limited, Bombay.
J Assoc Physicians India. 1991 May;39(5):403-7.
Interval data may be discrete or continuous. They are usually summarized by the average (arithmetic mean). Sometimes, for example when the possible values in a series change by a constant multiple, we need to use the geometric mean. To obtain the overall or mean percentage of a series of percentage values, we need to calculate their weighted mean. The variability of observations in a sample is measured by the standard deviation, and the variability of sample means is measured by the standard error of mean. Confidence interval is a range which contains the population mean with a known probability. It is obtained by deducting from the sample mean, and adding to it, "t" times the SEM, the value of "t" depending on the desired confidence level (1-P) and the sample size (N). The significance of difference between the mean of two sets of unpaired interval data (MA-MB) is tested by Student's t-test. If the data are paired, the significance of the mean difference (MD) is tested by paired t-test. Ordinal data, ie, grades and ranks, may be analyzed by means of the t-test which is more sensitive and allows more refined analyses if needed.
区间数据可以是离散的或连续的。它们通常用平均数（算术平均数）来概括。有时，例如当一系列中的可能值以恒定倍数变化时，我们需要使用几何平均数。为了获得一系列百分比值的总体或平均百分比，我们需要计算它们的加权平均数。样本中观测值的变异性用标准差来衡量，样本均值的变异性用均值标准误来衡量。置信区间是一个包含总体均值且具有已知概率的范围。它是通过从样本均值中减去并加上“t”乘以标准误得到的，“t”的值取决于所需的置信水平（1 - P）和样本大小（N）。两组未配对区间数据均值（MA - MB）之间差异的显著性通过学生t检验来检验。如果数据是配对的，平均差异（MD）的显著性通过配对t检验来检验。有序数据，即等级和排名，可以通过t检验进行分析，如果需要，t检验更敏感且允许更精细的分析。
