No Irrelevant Data

Variables that have no possible meaning to the user of the data file should be excluded from the data file, as the more junk in a data file, the:

• Harder it is to navigate.
• The slower it is for calculations to complete.

Examples of junk variables that are often included are:

• Panel management variables. For example, variables indicating the language, where they have the same value for everybody in the data set. 
• Looped variables that have one variable with a value of 1 for every respondent, another will have a value of 2 for all respondents, and so on.
• Variables representing un-used codes in multiple response questions.