1, variance is the measure of dispersion when probability theory and statistical variance measure random variables or a group of data. Variance in probability theory is used to measure the deviation between random variables and their mathematical expectations (that is, the mean value). The variance (sample variance) in statistics is the average value of the square of the difference between each sample value and the average value of all sample values.

2. Extreme range, also known as extreme range error or range, is represented by R, which is used to represent the difference between the maximum value and the minimum value of the measurement value of variance in statistical data, that is, the data obtained by subtracting the minimum value from the maximum value. Refers to the difference between the maximum value and the minimum value in a set of data.

3. Difference: Range is the difference between the largest number and the smallest number in a set of data, and variance is the sum of each number in a set of data minus the square of its average value and then divided by the number of data in this set.