ContentsComposite scores- One of the main flexibilities with a statistical package like SPSS (besides being able to conduct statistical analyses and obtain tabular and graphical output) is the capacity for manipulating data.
- One important data manipulation is the creation of new variables, which are some mathematical function of other variables.
- Psychological research often involves measuring fuzzy constructs, such as personality traits, by gathering responses to multiple items (such as questions in a survey) which are combined to provide a (hopefully) reliable and valid measure of a broader construct (such as extraversion).
- These "composite scores" can be:
- Unit-weighted, with the data from each item being equally weighted (by either adding all items together or calculating the average of each item), or
- Regression-weighted, e.g., from a factor analysis (not explained here).
Via pull-down menus- Make sure you have the data file open, then go to Data View (.sav)
- Enter new variable name in "Target Variable"
- Enter formula for creating composite score in "Numeric Expression"
To compute the score, click OK. Scroll to the right-hand side of the data file (in Data View) and you should see a new column. If the the new variable doesn't have any data, try saving your data file (which executes any pending calculations). If data appears, then its a good idea to run frequencies, descriptives, and/or an appropriate graph to check whether you have the kind of data you intended to create.
Via syntaxAn easy way to create the syntax commands is to follow the instructions above, but on the last step, click Paste instead of OK. The syntax can then be conveniently copied and edited - this is especially useful if you have many composite scores to calculate. It also allows the syntax commands to be saved (.sps) and recalled for later use. e.g.,
compute satistotl = satis+satis2+satis3+satis4+satis5. compute satismean = mean(satis1,satis2,satis3,satis4,satis5). Allow for missing valuesYou can allow for missing values by adding ".X" after "mean", where X is the minimum number of variables that need to have data for a case in order to calculate a mean. For example, this syntax will calculate a satis score for a case as long as it has at least 3 values of the variables listed:
compute satismean = mean.3(satis1,satis2,satis3,satis4,satis5). If a case has data for less than three of the variables, satis will be system missing (.). Otherwise, a mean will be created using data from all available variables.
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