Group spacing: (maximum quantity-minimum quantity)/group quantity

Probability: theoretical number of events A/ total number of events.

Mode: the abscissa of the midpoint of the bottom of the highest rectangle in the frequency distribution histogram.

Arithmetic average: the median of each group of values in the frequency distribution histogram is multiplied by the frequency and then added.

Weighted average: the weighted average is the sum of all frequencies multiplied by numerical values.

Median: the abscissa of a straight line parallel to the Y axis, which divides the histogram of frequency distribution into two parts with equal area.

Extended data

? In the rectangular coordinate system, the horizontal axis represents the continuous available values of the sample data. According to the minimum and maximum values of the data, the sample data are divided into m groups, so that the maximum and minimum values fall within the open interval (a, b), where a is slightly smaller than the minimum value of the sample data and b is slightly larger than the maximum value of the sample data.

The interval between groups is d=(b-a)/m, and the boundary range of each data group is left closed and right opened, such as [a, a+d], [a+d, a+2d), ... [a+(m- 1) d, b).

The vertical axis represents the value of frequency divided by the group distance (the number of sample data falling in each group is called frequency, and the frequency divided by the total number of samples is frequency), and in the rectangular coordinate system, it represents a rectangle with high quotient between frequency and group distance and the bottom of group distance, so the statistical chart drawn from it is called frequency distribution histogram.