Summary Measures for Scale Variables
There are many summary measures available for scale variables, including:
- Measures of central tendency. The most common measures of central tendency are the mean (arithmetic average) and median (value at which half the cases fall above and below).
- Measures of dispersion. Statistics that measure the amount of variation or spread in the data include the standard deviation, minimum, and maximum.
- Open the Frequencies dialog box again.
- Click Reset to clear any previous settings.
- Select Household income in thousands [income] and move it into the Variable(s) list.
- Click Statistics.
- Select Mean, Median, Std. deviation, Minimum, and Maximum.
- Click Continue.
- Deselect Display frequency tables in the main dialog box. (Frequency tables are usually not useful for scale variables since there may be almost as many distinct values as there are cases in the data file.)
- Click OK to run the procedure.
The Frequencies Statistics table is displayed in the Viewer window.
In this example, there is a large difference between the mean and the median. The mean is almost 25,000 greater than the median, indicating that the values are not normally distributed. You can visually check the distribution with a histogram.