A check which can be used to verify correct computations in a table of grouped classes. For example, consider the following table with specified class limits and frequencies . The class marks are then computed as well as the rescaled frequencies , which are given by
(1)

where the class mark is taken as and the class interval is . The remaining quantities are then computed as follows.
class limits  
3039  34.5  2  32  18  
4049  44.5  3  27  12  
5059  54.5  11  44  11  
6069  64.5  20  20  0  
7079  74.5  32  0  0  0  32 
8089  84.5  25  1  25  25  100 
9099  94.5  7  2  14  28  63 
total  100  176  236 
In order to compute the variance, note that
(2)
 
(3)
 
(4)

so the variance of the original data is
(5)

Charlier's check makes use of the additional column added to the right side of the table. By noting that the identity
(6)
 
(7)

connects columns five through seven, it can be checked that the computations have been done correctly. In the example above,
(8)

so the computations pass Charlier's check.