The New Zealand Qualifications Authority is commissioning an independent review of last week's Level 3 statistics exam, which contained an error.
It was also reviewing its quality assurance processes because of the error, as well as another error that occurred in a Level 2 maths exam last week.
The authority said the Level 3 mistake was the only error of significance under review that impacted on a candidate's ability to complete a question.
It was taking the matter very seriously, it said.