How to Compare Data Sets?
Common graphical displays (e.g., dotplots, boxplots, stemplots, bar charts) can be effective tools for comparing data from two or more data sets.
Four Ways to Describe Data Sets:
When you compare two or more data sets, focus on four features:
Center. Graphically, the center of a distribution is the point where about half of the observations are on either side.
Spread. The spread of a distribution refers to the variability of the data. If the observations cover a wide range, the spread is larger. If the observations are clustered around a single value, the spread is smaller.
Shape. The shape of a distribution is described by symmetry, skewness, number of peaks, etc.
Unusual features. Unusual features refer to gaps (areas of the distribution where there are no observations) and outliers.
The remainder of this lesson shows how to use various graphs to compare data sets in terms of center, spread, shape, and unusual features.