Starting with v18.06 Survey Solutions allows protecting values of trigger questions that have been preloaded from being subsequently modified by the interviewer. The protection applies to reduction, but permits extension. This is commonly needed in the panel surveys, where, for example, the names in the list of household members that are preloaded should not be eliminated by the interviewer, but new household members may be added if needed.

The protection applies to questions that may perform the role of triggers: 

• numeric, 
• text list, and 
• multiple-select categorical (in regular or Y/N-mode). 

Note also, that the answers to the questions may be protected even if they are not triggering any rosters, as long as the type of the question is one of these three.

If the answer to the question is protected, then:

• for numeric question the interviewer may specify an answer greater or equal to the one specified during preloading;
• for text list question the interviewer may append new items to the end of the text list, but not remove the ones that were preloaded;
• for multiple-select categorical question the interviewer may select any categories in addition to the ones already selected during preloading, but can’t unselect the pre-selected categories.
• for multiple-select categorical question in Y/N-mode the interviewer may change the selection of options that were preloaded as missing, but can’t change their selection if they were preloaded as either positively or negatively selected.

The protection of answers may only be done in advanced preloading mode when the identifying information and preloading data are uploaded as a single zip archive. To protect the answers an additional text file with the name protected__variables.tab (mind the double underscores in the file name) must be created and placed into the zip-archive alongside the main data file there. This file has the following structure: the 1st line should contain exactly this word: variable__name, while the 2nd, 3rd and subsequent lines should contain variable names of the questions that need to be protected (each variable on it’s own line). For example:

variable__name
hhmembers
n_parcels
n_crops

The protection applies to the variable specified, regardless of the level where it is positioned in the questionnaire, whether in the main level of the interview, in a roster, or in a nested roster. In the above example, the n_crops variable may be the trigger for the crops roster nested into the parcels roster, and the answers to n_crops specified in any parcel will be protected.

If the Survey Solutions identifies a problem with this file, it reports an error and aborts the preloading process. For details, see the following troubleshooting reference.

This protection of answers is effective in the whole set of data being preloaded. Note that the empty answers are not protected (e.g. if numeric question was not preloaded, the interviewer will be able to specify any value).