Frequency is also the number of events, and the interval between groups is the distance between histograms. In general college entrance examination questions, the frequency is given in the form of histogram, and then there is a relationship: (frequency/interval), and then the value above the histogram is equal to the frequency/interval, which means the required frequency needs to be calculated. The specific algorithm is to multiply the value above the histogram by the interval (the interval can be obtained according to the observation map) and adopt it.