Making Boxplot Graphs:

Click on Graphs in the top menu bar of the Data View window. From the drop down menu select Boxplot...>>>

Select Clustered from the Boxplot dialog box then click Define. Note: I left the default radio button checked (Summaries for group cases).

In the Define Clustered Boxplot dialog box move (Plant Growth) into the Variable: box, Light into the Category Axis: box and Fertilizer into the Define Clusters by: box. Click on the Options button and in that dialog box check Display groups defined by missing values then click Continue.

Clustered boxplot graphs show an interaction between the light and fertilizer treatments in their effect on plant growth (N. Clifford and G. Valentine p. 332).

I found several on-line tutorials for how to use SPSS. One in particular, Texas A&M University, has a video clip library that anyone can access (Texas A&M University, SPSS Tutorials).

Works Cited

Clifford, Nicholas J., and Gill Valentine. Key Methods in Geography. London: Sage Publications, Ltd., 2004.

(McGrew, Jr. J. Chapman Monroe Charles B. Introduction To Statistical Problem Solving in Geography 2000)McGrew, J. Chapman, and Charles B. Monroe. An Introduction To Statistical Problem Solving in Geography. 2nd ed. Boston: McGraw-Hill Companies, Inc., 2000.

(SPSS for Windows: Getting Started Information Technology Services 13 September 2001)SPSS for Windows: Getting Started. Ed. Information Technology Services. 13 September 2001. The University of Texas at Austin. 15 Mar. 2006 <http://www.utexas.edu/its/rc/tutorials/stat/spss/spss1/index.html>.

SPSS Tutorials. Ed. Department of Statistics. 2005. College of Science, Texas A&M University. 15 Dec. 2006 <http://www.stat.tamu.edu/spss.php>.