How To Create An Index In Stata

To create your Index question, you can use all categorical questions and not only scale questions. Indexes can be shown as a percentage or mean and you can also add weight to the indices. The Index question function can be found on the New Variables/Values. Pressing the Index question tab will take you to Index menu where you need to assign Code, select color and Report text as well as select variables to create Index.

To create a new variable, click the "Create new variable" option in top left corner, in the resulting popup, select what type of variable to create, then continue to create the new variables. Select the third option to create the Index variable.

Here we see the option for selecting the type of variable to be created.

To edit, or delete, an already created compute, index or merged variable use the edit and delete icons displayed in the most right column of the Question grid, see example of these icons in the image below.

Here we see how the edit and delete icon appears for computed, merged and index variables.

Input a Code in text form by typing your new Code.
Select Color template code from the drop-down menu.
Select variables which will form your Index question
Press Apply
Select the Answer block available for your selected Variables
Input a Weight value for the selected variables (total should add up to 1)
Press Save

This creates your Index question, which you can review by going to Edit Index Questions page, next to Create New page.

For ease of use the questions can be filtered by question blocks for faster selection.

At the bottom of the index creation page an option to apply an equal weight per question can be found which speeds up the process as it is automatically set to equal weight on all ingoing questions if all questions should have the same impact on the index.

Respondent Level:

The calculation is made on respondent level as previously the index was calculated on respondent level when weight columns was left empty.

Average:

All ingoing questions will have an equal weight when this option is selected.

Weighted average:

Specify the desired weight per question like before, the sum of all weights should be equal to 1.

Notes

Index questions can only be based on categorical questions
All selected questions need to have the same number of answer alternatives. If questions with a different number of answers are selected, a warning message will appear and the index won't be saved.
Index questions can't be used as filter.
Index is an aggregated score which cannot be used in a respondent table.