Errors in data entry or column shifts in subsequent
processing is often easy to detect, since there may be a response such as 3 or 4
appearing to a question which only allows 1 or 2 as a valid response. Correction of this error warrants having the actual completed
survey forms available during the data cleaning stage of analysis. Although rare, these errors can play havoc with analysis if
undetected. When they are detected in one variable, other variables in the affected cases should be carefully checked.