| Class | 0-99 | 100-299 | 300-499 | 500-749 | 750-899 | 900-999 |
| Frequency | 10 | 12 | 14 | 16 | 8 | 10 |
= 0.5 from the lower limit of each class and adding it to the upper limit of each class. we yet lower boundary point and upper boundary point respectively for each class, which is shown in the table on page 28.| Class | Class length = (Upper class boundary point – lower class boundary point ) | Mid value =  |
Frequency |
| -0.5-99.5 | (99.5 – (-0.5) = 100 |  = 49.5 |
10 |
| 99.5 -299.5 | (299.5 – 99.5) = 200 |  = 199.5 |
12 |
| 299.5 -499.5 | (499.5 – 299.5) = 200 |  = 399.5 |
14 |
| 499.5 -749.5 | (749.5 – 499.5 ) = 250 |  = 624.5 |
16 |
| 749.5 – 899.5 | (899.5 – 749.5) = 150 |  = 824.5 |
8 |
| 899.5 – 999.5 | (999. 5 – 899.5) = 100 |  = 949.5 |
10 |
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| Particulars | Series A | Series B |
| No. of observations | $40$ | $50$ |
| Average | $25$ | $30$ |
| The sum of squares of deviations taken from mean | $640$ | $1800$ |