I was somewhat surprised to learn today that Kathleen Tattersall, the chairwoman of Ofqual, England's new examinations regulator, has apparently announced that some GCSE and A-level exam results may not be entirely accurate. While this relates primarily to the education system in England, Wales and Northern Ireland, some schools in Scotland offer courses leading to these qualifications.

As all teachers/lecturers in the education system well know, it is possible to achieve exactness in marking exams in precise sciences, such as mathematics and physics. Exactness is also theoretically possible in examinations assessed by a multiple choice system, provided the questions and presented alternatives are themselves accurate.

However, it is equally appreciated that many subjects do not lend themselves to the same degree of precision - two obvious ones being English and history, where the answers will be of the essay type. It is in these areas where there must be, and always will be, an element of variation between exam assessors, so that exactness is not feasible. However, if the examination assessors are of suitable ability and experience, this variation should be minimal, and statistically non-significant.

The main problem with Ms Tattersall's remark is that she made it at all. She has sown the seeds of doubt in a fertile plain of suspicion - where students and relatives may be all too willing to question or challenge a disappointing exam result.

This was her big mistake.

Dr Neil C Scott, 76 Carnbee Park, Edinburgh.