1. How to find measures variability using SPSS
Lesson 3 in SPSS
How to find measures variability using SPSS

2. The Dataset Here’s a nice dataset. We have one variable called Age.
There are 1,514 observations in the dataset.

3. First Blush
To get a quick picture of this dataset, let’s see a frequency distribution histogram (Lesson 1).
Hmm, perhaps a bit skewed?

4. Selecting the Analysis
From the SPSS menu bar, choose
Analyze
Descriptive statistics
Frequencies

5. Select the Variable(s)
In the Frequencies box, highlight the variable age, then click on the arrow to pop it into the Variables window.

6. Descriptives Box
Notice that when you’ve done this, the OK box is now active.
But let’s make sure we get the statistics we want.

7. Selecting the Statistics
I’ve selected the mean, median and mode as my measures of central tendency. Plus, I asked for the sum.
For my measures of spread, I’ve chosen standard deviation, variance, and range. Plus I asked for the minimum and maximum values.

8. The Interquartile Range
To find the interquartile range in SPSS, select Quartiles.
I’ve also asked it for a measure of the skewness of the distribution.
Now click on Continue.

9. Running the Analysis
Now we can click on OK.

10. The Output So what did we learn?
The mode is 35, the median is 41.00, and the mean is These measures appear to be the perfect definition of a positively skewed distribution.
The range is 71 and goes from a minimum of 18 years to a maximum of 89 years old.
The sample variance is and taking the square root of that we have the sample standard deviation of 17.81

11. More Output
To find the inter-quartile range, we take the 75th per-centile minus the 25th percentile. Here, it is 60 – 32 = 28. So the SIQ = 28/2 = 14.
Also, we note our skewness value is .524 with a standard error of Don’t worry about that now, we’ll look at this again in Lesson 4.

12. Visual Representation
Median
Mode
Mean
Mean
Let’s mark these on our graph.
SIQ = 14
s = 17.81
Range = 71