Log in to SPSS. Open the file that you saved under the name Questionnaire Data from last week. Select the radio button Open an existing data source in the SPSS opening window and highlight the filename. It may be necessary, especially in a networked computer, to select the More Files… option and select another disk drive or folder. Alternatively, select the Type in data radio button to open Data View, choose File, click Open, and finally Data to open the Open File selection box. Change the Look in: selection to the folder and/or disk drive where the file has been stored, click the filename so that it appears in the Filename box, and then Open. Your file should appear in Data View.

Locating the larger data set

The file containing the large data set with which you are going to merge your own data is to be found at the following WWW address:
        The dataset

in the file labeled EX_Data data. If this file has not already been downloaded on to a file server or hard disk drive for easier access, save the file to a more convenient place such as your hard disk drive.

Merging your data with the larger data set

To carry out the file merge, select Data, Merge Files, Add Cases... to obtain the Add Cases to [Your File Name] selection box, which prompts you to specify the file (the large data set) from which you want to merge other cases with your own. Click the An external SPSS data file radio button and then click Browse… to locate the file EX3_Data.sav and click the file name so that it appears in the panel. Click Continue to open the Add Cases From EX3_Data.sav dialog box (see Figure 1).

If you have entered the correct variable names in your own data file, the Add Cases From dialog box should show no variable names in the Unpaired Variables: box and all the other variable names should be in the Variables in New Working Data File: box.

Suppose, however, there had been a mismatch between one of the variable names you had typed into Data View and the name of the corresponding variable in the large data set. Suppose that, when you were building your Questionnaire Data, you had typed Ages instead of Age. The variables Ages and Age would both have appeared in the Unpaired Variables: box. You would have then had to select Ages and click Rename to obtain another dialog box, allowing you to rename it as Age. The correct variable name Age would then be transferred to the list in Variables in the New Working Data File.

Click OK to merge the files.

A warning

In the large data set, the Faculty variable was of the numeric type, with values assigned as follows: 1 = Arts, 2 = Science, 3 = Medicine, 4 = Other. Suppose that you had inadvertently assigned 1 to Science and 2 to Arts, instead of the other way round, and that as a science student, you had recorded a 1 in your own data set. SPSS will not warn you of the discrepancy. Instead, it will adopt your convention throughout the merged data set and all those people who recorded 1s in the larger original data set will now be recorded as scientists, not arts students. You can confirm this by choosing Value Labels from the View menu. All those previously recorded as science students will now be recorded as arts students and vice versa. When two files are being merged, it is the value assignments in the first file that determine those for the entire merged file, even when, as in the present example, the former contains only a single case.

revised 09-10-2009