In 2003, a researcher was responsible for coordinating the data collection among family members of the primary respondents to a study. Among those that they had to approach for participation in the survey were randomly selected siblings for which the primary respondents had provided contact information.

The siblings’ contact information was stored in an Excel file in order to make stickers for envelopes and questionnaires that were sent out to them. The targeted siblings were informed that their [brother / sister] born on [dd.mm.yyy] had given the researchers their contact details. However, right before printing the stickers, the researcher in charge sorted the data by date of birth, or so they thought. In fact, they had only sorted the column with the birth dates and nothing else. The result was that thousands of people received a letter that their sibling with a completely wrong date of birth had registered them for the study which resulted in a lot of upset calls and emails. People thought they had a sibling they didn't know about or that their father had another family.

The researchers had to reconstruct and manually correct the data using the original paper questionnaires and then re-sent all the letters together with a letter of apology.

This example shows that master data files should never be overwritten and that extra care needs to be taken when handling personal information!