Adjustment in Class Interval

When a continuous variable is classified by the inclusive method, as in Table 3.4 above, the classes leave visible gaps. Between the upper limit of one class (899) and the lower limit of the next (900) there is a gap of 1, which breaks the continuity the variable should have. The gap is closed by an adjustment:

1. Find the difference between the lower limit of a class and the upper limit of the previous class: $900-899 = 1$.
2. Halve it: $1/2 = 0.5$.
3. Subtract 0.5 from every lower limit.
4. Add 0.5 to every upper limit.

This gives the continuous (exclusive) form:

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