Since survey data collection requires the work not
only of the survey administrator, data entry person, and often a translator,
there are many opportunities for error in coding the responses to the questions. Errors can occur during the data collection stage,
in recoding forms, or during data entry. If the results are not out of range, then they may be difficult to detect in examining the
variable itself. The error may appear when bivariate associations and possible outliers are examined by scatterplotting.