Bar Charts, like pie charts, are useful for comparing classes
or groups of data. In bar charts, a class or group can have a
single category of data, or they can be broken down further into
multiple categories for greater depth of analysis.
Things to look
Bar charts are familiar to most people, and interpreting them
depends largely on what information you are looking for. You
might look for:
- the tallest bar.
- the shortest bar.
- growth or shrinking of the bars over time.
- one bar relative to another.
- change in bars representing the same category in
- Watch out for inconsistent scales. If you're comparing two or
more charts, be sure they use the same scale. If they don't have
the same scale, be aware of the differences and how they might
trick your eye.
- Be sure that all your classes are equal. For example, don't
mix weeks and months, years and half-years, or newly-invented
categories with ones that have trails of data behind them.
- Be sure that the interval between classes is consistent. For
example, if you want to compare current data that goes month by
month to older data that is only available for every six months,
either use current data for every six months or show the older
data with blanks for the missing months.
For each bar in the bar chart, the following statistics are
||the average height of all the
||the maximum value (tallest bar) in
||the minimum value (shortest bar) in
||the number of values (bars) in the
||the maximum value minus the minimum
||Indicates how widely data is spread
around the mean.