A SUM is a combination of other categories where the tables involve Numeric Questions.
The SUM is computed by:
- Identifying observations with no missing data.
- Computing the sum of the values for each of these obsevations (excluding any SUM categories on the table that have been created using Create NET).
- Taking the average of these sums.
Creating a SUM
SUMs are automatically created when a project is setup in in Q. Further SUMs can be created on Numeric Questions by selecting multiple categories, right clicking and selecting Create NET (see Manipulating Data).
The SUMs that are automatically created (i.e., which, by default, are shown at the base and to the right of tables) are no different to SUMs that are manually created using Create NET.
SUMs are computed first at the respondent level, and then the average of these totals are shown on the table. Where there is missing data for any of the respondents in a SUM, the SUM will exclude the data for that respondent. You can check if this is occurring using Statistics - Cells > Base n (see also Sample Size Seems Too Small). Where this is not appropriate, you can:
- Use Rules.