Class Boundaries

Updated 15 Sep 2026

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What it is
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  the precise dividing points between classes, adjusted (e.g. by half a unit) so that classes have no gaps and no overlap between them
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Distinguish from
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  Class Limit — the class limits as originally stated (e.g. "1–4," "5–8") can leave small gaps between classes; class boundaries close those gaps
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Formula
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  $L_b$ (lower boundary) = class's stated lower limit − $\frac{1}{2} \cdot$ (smallest unit of the data)
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  $L_a$ (upper boundary) = class's stated upper limit + $\frac{1}{2} \cdot$ (smallest unit of the data)
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  e.g. for data recorded to 1 decimal place, the smallest unit is 0.1, so boundaries adjust by 0.05
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Related
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  Frequency Distribution

Linked references 2