In this Example we have three columns, in the first column we have marks obtained by the students from range 0 - 30, 30 - 60 and so on, we have another column of frequency i.e. 2, 6, 4, 8, 10, 12, 14, 16 and last third column is of calculation of cumulative frequency. The first value of Fc is 2 after that we have second value, that is Sum of 2 (Fc) and 6 (second value in Frequency column) is 8 that is the cumulative frequency (Fc). Similarly we have the second cumulative frequency as 16, which is sum of 8 (Second cumulative frequency) and 8(the third value of the frequency column).
Similarly we can calculate cumulative frequencies of all values in table from range of obtained marks 0 - 30 to 180 - 210.
Cumulative frequency is used for calculating reliability analysis. From reliability analysis it gives the total number of events occurred up to given values in analysis table.
The graph of cumulative frequency gives a proper description of the analysis made.