How to Construct a Weight for a Self-Weighting Sample

Related Online Training modules
Deleting Individual Observations
Deleting Multiple Observations
Modifying a .sav file
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Sometimes there is a need to create weights using data which includes people that screened out of a study. For example, the first two questions may be age and gender and the third question the screener, but there is a need to weight the age and gender to the entire population. This is done as follows:

1. Obtain a data file that includes the data for the respondents that were screened out but need to be taken into account when creating the weight.
2. Create the weight.
3. In the Variables and Questions tab, right-click on the weight variable and select Copy and Paste Variable(s) > Linked.
4. In the Variables and Questions tab, right-click on the new variable and select Convert Formula to Fixed Data.
5. Tag the new variable as a weight
6. Delete the respondents that screened out.
7. (Optionally) If the data file is huge, Save the data as an SPSS data file and the re-import.

Rescaling the weight so that has an average of 1.0

If you wish to rescale the variable so that it has an average of 1.0:

1. In the Variables and Questions tab, right-click on the weight variable and select Copy and Paste Variable(s) > Linked.
2. Right-click on the newly created variable and select Edit Variable.
3. Update the Expression. For example, if the Expression is wQPVSF, and its Mean is 0.0275 (shown at the bottom of the dialog box), your expression would be wQPVSF / 0.0275. (If you wish to compute the average with more decimal places, create a table in the Outputs Tab and increase the number of values.)
4. Press OK.
5. Tag the new variable as a weight

Automatically completing the above steps

If this process needs to be done automatically as a part of a tracking study this can be done using Access all data rows but this is a very complicated process (as you will need to create the weights using formulas written in JavaScript).