How to Analyze a Continuous Variable in Spss

To call the Frequencies procedure, clickAnalyze > Descriptive Statistics > Frequencies.

A Variable(s): The variables to analyze with the Frequencies procedure. To include a variable for analysis, double-click on its name to move it to the Variables box. You can add several variables to this box to obtain statistics for each variable.

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B Statistics: Opens the Frequencies: Statistics window, which contains various descriptive statistics, most of which are suitable for continuous numeric variables.

Most of the statistics in the Central Tendency, Dispersion, and Distribution groups are valid for continuous variables; the only exception is the Mode, which very rarely has a useful interpretation for situations involving continuous variables. Most of these statistics are identical to the ones that can be obtained with Descriptives, Compare Means, or Explore, so they will not be covered again here. One noticeable exception to this is the Percentile Values group, which is unique to the Frequencies procedure:

• The Quartiles option produces the first, second, and third quartiles (i.e., the 25th, 50th, and 75th percentiles, respectively).
• The Cut points for n equal groups option will divide the dataset into n equally sized groups and report the percentiles. For example, if the user specifies n=5, then the output will report the 20th, 40th, 60th, and 80th percentiles. Or, if the user specifies n=10, then the output will report the 10th, 20th, 30th, ..., 90th percentiles.
• The Percentiles option allows the user to specify the exact percentiles to report. The percentiles should be entered as whole numbers.

You can select more than one option in the Percentile Values group. If your selections request overlapping information, that information will not be printed twice.

Note: The Values are group midpoints check box should only be selected when your data values represent the midpoint of a range. For example, this would be the case if you had coded anyone between the ages of 30 and 39 as 35 (source: IBM SPSS Statistics Information Center). This situation is more often associated with ordinal categorical variables.

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C Charts: Opens the Frequencies: Charts window, which contains various graphical options. Options include bar charts, pie charts, and histograms. Histograms are the only appropriate option for continuous variables; bar charts and pie charts should never be used with continuous variables. If requesting a histogram, the optional Show normal curve on histogram option will overlay a normal curve on top of your histogram, which can be useful when assessing the normality of a variable.

Note that the options in the Chart Values area apply only to bar charts. These buttons will be greyed out if the radio button for Histograms is selected.

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D Format: Opens the Frequencies: Format window, which contains options for how to sort and organize the table output.

The Order by options are not relevant to continuous variables, but the Multiple Variables options allow for customization of output when two or more continuous variables are specified.

• Compare variables places the descriptive statistics for the numeric variables side-by-side
• Organize output by variables creates separate summary tables for each numeric variable.

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E Display frequency tables: When checked, frequency tables will be printed. (This box is checked by default.) If this check box is not checked, no frequency tables will be produced, and the only output will come from supplementary options from Statistics or Charts. You will want to uncheck this box if using the Frequencies procedure on a continuous numeric variable. (If this box is left checked, a frequency table will be produced where each unique number is treated as its own category. This could lead to a table with 100+ categories, depending on the number of observations in your dataset.)

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Source: https://libguides.library.kent.edu/SPSS/FrequenciesContinuous

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