In this post you will learn how to create a boxplot in spss.
Boxplot –
A boxplot or box-whisker diagram is a really useful way to display your data. At the center of the plot is the median, in a box the top and bottom of which are the limits within which the middle 50% of observations fall (the interquartile range, IQR). Sticking out of the top and bottom of the box are two whiskers which show the top and bottom 25% of scores (approximately).
Let’s read a dataset to create a Boxplot. click here to download
Open spss and go to file > open > data and from the dialog box select the downloaded data.
The data will look like this –
To create a Boxplot in SPSS, click on Graphs > chart builder. Then from the gallery select boxplot.
There are three types of boxplot you can choose –
- Simple Boxplot – Use this option when you want to plot a boxplot of a single variable but you want different boxplots produced for different categories in the data.
- Clustered boxplot – This option is same as the simple boxplot, except that you can select a second categorical variable on which to split the data. Boxplots for this second variable are produced in different colors.
- 1-D Boxplot – Use this option when you want to see a boxplot for a single variable. This differs from the simple boxplot in that no categorical variable is selected for the x-axis.
In the data file of success scores we have information about whether people worked hard or wished upon a star. Let’s plot this information. To make a boxplot of the post-intervention success scores for our two groups, double click on the simple boxplot icon, then from the variable list select the Success_Post variable and drag it into y-axis and select the variable Strategy and drag it to x-axis. The dialog box should look like this
Click on OK to create the boxplot.
The above figure shows the boxplots for the success data. Notice that there is a tinted box, which represents the IQR (i.e. the middle 50% of scores). It is clear that the middle 50% of scores are more spread out for the hard-work group than for those who wished on a star because the box is much longer. Within the box, there is a thick horizontal line, which shows the median. The workers had a higher median than the wishers, indicating greater success overall. The top and bottom of the tinted box represents the upper and lower quartile respectively. The distance between the top of the box and top of the whisker shows the range of the top 25% of scores (approximately), similarly the distance between the bottom of the box and the end of the bottom whisker shows the range of the lowest 25% of scores (approximately).