2. Arithmetic average: the median of each group of values in the frequency distribution histogram is multiplied by the frequency and added. ?
3. weighted average: weighted average is the sum of all frequencies multiplied by the value? .
4. Median: the abscissa of a straight line parallel to the Y axis, which divides the frequency distribution histogram into two parts with equal areas.
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).
2. 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. In many practical problems, it is of great significance to study variance or deviation. Variance is a measure of the difference between the source data and the expected value.