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Lesson 3 in SPSS

Lesson 3 in SPSS. How to find measures variability using SPSS. The Dataset. Here’s a nice dataset. We have one variable called Age. There are 1,514 observations in the dataset. First Blush. To get a quick picture of this dataset, let’s see a frequency distribution histogram (Lesson 1).

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Lesson 3 in SPSS

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  1. 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 45.63. 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 317.14 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 .063. 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

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