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Unexpected missing answers


In our last CATI studies we have encountered a problem: we found in the databases missing answers for questions that should have been answered. We had unique passwords in all of our studies (1 password per respondent). In order to find the bug, we tested both locally and online on the exact passwords with which we had problems and the all the questions appeared.

The variable sys_UserAgent - for the problematic cases -   generally records this type of information
-"Mozilla/5.0 (X11; Linux i686; rv:7.0.1) Gecko/20100101 Firefox/7.0.1"
-"Mozilla/5.0 (Ubuntu; X11; Linux i686; rv:9.0.1) Gecko/20100101 Firefox/9.0.1"

We are using SSIWeb v7.

We believe the problem might be between the current SSIWeb version and the software used, but we didn't manage to find the exact problem.

Did anybody else encounter this problem?

Thank you,
asked Mar 8, 2012 by anonymous

3 Answers

+2 votes
Did you check the limbo files on the server for that study?  Almost anytime I've had missing data I've been able to find it in the limbo files.
answered Mar 8, 2012 by Jay Rutherford Gold (38,800 points)
if I remember correct limbo files are created when the respondent backtracks through the survey. they store data for the initial flow of the survey and if and when the flow changes, limbo data should be irrelevant? is that not the case?
That is where they have directed me on the occasions I have had missing data in my exported datasets.
Thank you for your help! Jay you were spot on :) I managed to recover my data.

Still a question remains: until now we didn't have this sort of problem. It only appeared after we changed the server to Linux. As Linux writing privileges are set manually, could this be the issue that generates this problem? Maybe the software tries to get data from the limbo file and because of the restrictions it can not (if I'm not mistaken about the way limbo files work:) ).
Not sure about that, but in version 8 there are no more limbo files as they do not expect that problem to occur anymore with the current database format (at least that's what I've been told).
Jay you are correct.  However, there is still a backup of all the data in the history table of the study where data is never deleted.  So if for some reason in V8 the data does ever go missing, you could check there.  So far we haven't heard of any missing data in V8
I still got missing information in data table but exists in history... especially with quota enabled studies - reminding bug fixed @ SSI Web 8.1.2 (22 Oct 2012)

Running on 8.3.6.
+1 vote
we've sometimes observed this and still don't know the exact reason. but I suspect sometimes the server gets too busy and some respondents data is lost in this time. this is just speculation.
answered Mar 8, 2012 by Bahadir Ozkurt Gold (17,010 points)
+1 vote
Please send any missing data issue like this to support@sawtoothsoftware.com.  We will take a look at it and get back to you.
answered Mar 8, 2012 by Justin Luster Silver Sawtooth Software, Inc. (7,875 points)