A class interval is an interval in statistics representing a range of numbers.
Class intervals either include
This example shows a chart where the intervals include both endpoints.
The interval $5.00–$9.99, for example, means that any CD costing anywhere from $5.00 up to and including $9.99 would be counted in this price range.
A "gap" occurs between $9.99 and $10.00 since there are no coins to represent amounts less then one cent. No amount like $9.993 could be exactly paid for.
This example shows a chart where the intervals include only the bottom endpoint of the range.
The interval 130–133.5, for example, means that any height of 130 cm up to but not including 133.5 cm would be counted in this height range. This is done so that no height is counted twice. A height of 133.5 cm would be included in the 133.5–137 interval, not in the 130–133.5 interval.
There cannot be a "gap" since a height could always be measured that might fall into one of the gaps.
