Knowing what was done: uses of a spreadsheet log file

Spreadsheet use in educational environments has become widespread, likely because of the flexibility and ease of use of these tools. However, they have serious shortcomings if the teacher is to understand exactly what students or others have done. It is far too easy for students to replace a formula that gives an apparently unacceptable answer with a number that they believe to be correct. The same concern applies to recorded marks, as well as to business spreadsheets and to other reports that are used for decision-making. While intentionally misleading changes to spreadsheet files receive much attention, simple mistakes are probably more common. Some of these, such as the Trans-Alta Utilities (Globe and Mail, 2003) cut and paste error that cost the firm $24 million (US), have extreme consequences. Few are merely embarrassing. A log file or audit trail, enhanced by suitable filters, can allow both intentional and accidental changes that cause erroneous results to be caught. We have developed such a tool – TellTable – and are currently beginning to apply it in various application environments, including our own teaching. Preliminary reactions to the tool are reported.