Type of Data Being Counted

There are two types of data that can be represented on bar graphs. One is ordinal data, the other is nominal data.

Data characterized as ordinal has: Groups that should be listed in specific order. The order may be either increasing or decreasing. The data could have numeric values, or values such as high, medium, low. One example would be exam grades, another example could be price levels. Ordinal data allows us to look at trends as we move along this axis. As we can see, in this graph, the data has a numerical order. The data groups are numerical amounts that go from a low of $1 to a high of $5.

Data characterized as nominal has: Data groups that do not have a specific order. An example of this could be country names, or individuals, or, as shown on the right, Courses by name. These don't need to be placed in any order. With nominal data you can only make statements about the difference between groups, and comment on patterns, such as in the example on the right. Note that the inferences we draw from the data are different for ordinal and nominal data. For example, with ordinal data you can look at trends.

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