Class Mark

Here we will learn class mark.

The class mark of a class interval = \(\frac{\textbf{Actual lower limit + Actual Upper Limit}}{2}\)

                                                 = \(\frac{\textbf{Sum of Class Boundaries}}{2}\)

For Example:

The class mark of the overlapping class interval 10 – 20

                                                                    = \(\frac{\mathbf{10 + 20}}{2}\)

                                                                   = 15.

The class mark of the overlapping class interval 11 – 20 (when the intervals are 1 – 10, 11 – 20, 21 – 30, etc.)

                                                                   = \(\frac{\mathbf{10.5 + 20.5}}{2}\)

                                                                   = 15.5

Note: Through in a grouped data the class intervals can be of unequal size, usually we will meet class intervals of equal size. In case of nonoverlapping intervals, the gaps between consecutive intervals may be unequal. But at this level we will deal with intervals with equal gaps between consecutive classes. In such cases,

Class size = Actual upper Limit – Actual lower limit, and        

Class Mark = \(\frac{\textbf{Lower limit + Upper limit}}{2}\)

9th Grade Math

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