Special Code Values in Automatic Variable Calculations

Collected data may include various types of missing values which are expressed as special codes in QDS, such as Don’t Know, Refused to Answer, and Not Applicable. Each of these is a form of missing data (see Missing Values, regarding how to assign a missing value as part of an Automatic Variable calculation). Also, Data Elements may be skipped during an interview based on programmed skip patterns. Mathematical operations performed by QDS are able to handle the different types of missing data in ways that you can specify for each Data Element.

QDS treats each Data Element not as a single value, but as a range of allowable values as defined for the element in the specifications. The response can be an allowable value, one of the allowed special codes (Don’t Know, Refused to Answer, Not Applicable), or a Skipped code. Allowable ranges for responses are listed in Skip-Edit Check Reports and in response data in the Preview Tool.

You may specify how a missing item should be treated in numerical calculations on the Calculations tab for that Data Element. The default values are to treat Don’t Know and Refused as “Allowable range” and to treat Not Applicable and Skipped as zero (the default setting on the If Skipped tab indicates that skipped should be treated at Not Applicable).

When special codes are treated as "Allowable range", no value is substituted in a calculation – the calculation result will be missing.

You can also change any of the special codes to be treated as specified value or limited range when performing interim calculations. The specified range is entered in the boxes to the right of the special code. To specify an exact value, enter that value in both the From and To boxes.

Tip: These instructions affect only the value used in performing internal calculations and do not alter the value stored in the data file.