![]() ![]() In our data set, case number 40 is an extreme outlier. SPSS gives us the case numbers for these values. Extreme outliers: Values that are more than 3.0 x IQR below Q1 or above Q3 are represented by asterisks.In our data set, case number 4 is a mild outlier. Mild outliers: Values that are more than 1.5 x IQR below Q1 or above Q3 are represented by circles.This is the middle 50% of the data set (between Q1 and Q3). Interquartile range (IQR): The box in the boxplot.Maximum value that isn’t an outlier: Represented by the top of the vertical line (whisker) that extends from the top of the box.Third Quartile (Q3): The value below which 75% of the values in the data set are found.Median: The value that separates the higher half of the data set from the lower half.First Quartile (Q1): The value below which 25% of the values in the data set are found.Minimum value that isn’t an outlier: Represented by the bottom of the vertical line (whisker) that extends from the bottom of the box.The boxplot for students’ Statistics final exam scores created in SPSS is below.Īs you can see, boxplots illustrate the following values for a variable: Five Number Summary The SPSS Output Viewer will pop up with a “Case Processing Summary” and a boxplot for your variable. Select the variable for which you wish to create a boxplot (“Statistics Final Exam Score” in our example) and use the arrow button to move it to the Boxes Represent box. It is a good idea to click the Reset button to clear any previous settings. This brings up the “Define Simple Boxplot: Summaries of Separate Variables” dialog box illustrated below. Under “Data in Chart Are,” select Summaries of separate variables. This brings up the following “Boxplot” dialog box: (Note that if you are using SPSS version 28 or earlier, you will need to click Graphs -> Legacy Dialogs -> Boxplot). The easiest way to create a boxplot is to click Graphs -> Boxplot as illustrated below. We will generate a boxplot so that we can visualize the way in which these exam scores are distributed and determine whether they include any outliers. ![]() Our fictitious data set contains the Statistics final exam scores for 60 students (first 21 records displayed). (Check out our tutorials on importing data from Excel or MySQL into SPSS). The starting assumption for this tutorial is that you have already imported your data into SPSS, and that you’re looking at something like the data set below. Select the variable for which you wish to create a boxplot, and move it into the Boxes Represent box.Select Simple and Summaries of separate variables.Click Graphs -> Boxplots in SPSS version 29Ĭlick Graphs -> Legacy Dialogs -> Boxplots in earlier versions of SPSS. ![]()
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