I was asked such a question as "Did you do any consistency check in your daily work?" during a phone interview for a Biostatistician position. I don't know what to answer. Any information is appreciated.
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To chl's list, which focuses on frank data processing errors, I would add checks for subtler errors to address the following questions and issues (given in no particular order and certainly incomplete):
Perhaps the best kind of general "consistency check" anyone can perform is to graph everything, early and often.
I suppose this has to do with some form of Quality Control about data integrity, and more specifically that you regularly check that your working database isn't corrupted (due to error during transfer, copy, or after an update or a sanity check). This may also mean ensuring that your intermediate computation are double-checked (either manually or through additional code or macros in your statistical software).
Other information may be found here: the ICH E6 (R1) reference guide about Guideline for Good Clinical Practice from the EMEA, Guidelines on Good Clinical Laboratory Practice, or Clinical Research Study Investigator's Toolbox.
to add to the other good points
When using Excel, I always generate a case number as the first column for each line, this is then copied to the last column. Excel seems quite happy to sort just a few columns at a time, causing chaos if you are not careful to select them all. Your may not even be aware that this has happened. Being able to check that the case numbers agree in the first and last columns of a line is a useful precaution.
I always review the outliers.
Double entry of data by separate people is recommended for critical work.
When entering data from paper documents, it is a good idea to use a reference identifier to be able to refer back to the exact document and line from which the entry derived, numbering of data entry forms helps with this.
Edit - Another item - I know that editing spreadsheets is fraught with problems, but it is much easier to clean up data entry with them. However, I also keep the original unedited version, so that any changes can be verified or in the worst case restored.