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| Cumulative Frequency Distribution |
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| Cumulative frequency is obtained by adding the frequency of a class interval and the frequencies of the preceding intervals upto that class interval. This is explained by an example below. |
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| The following frequency distribution table gives the marks obtained by 40 students: |
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| Table (a) |
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| The frequencies can be added, as indicated by the arrows, to obtain the cumulative frequency. |
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| In the table(a), it is observed that 4 students got marks 'less than 10', 9 students got marks 'less than 20' and so on. |
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| Therefore, the above distribution is called 'less than' cumulative frequency distribution. |
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 Table (a) can be re-written as table (b). |
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| Table (b) |
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| In the same way 'more than' cumulative frequency distribution can be obtained by adding to the other frequencies in the reverse order. |
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| Table (c) |
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| The frequencies can be added, as indicated by the arrows, to obtain the cumulative frequency. |
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| Table (c) can be re-written as table (d) |
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| Table (d) |
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