A botch-up in a level 3 maths exam left thousands of students "stumped", and many "freaking out".
The New Zealand Qualifications Authority (NZQA) this morning admitted there was an error in a table in yesterday afternoon's statistics paper, and apologised for the mistake.
About 15,000 students sat the exam, and all were unable to provide a correct answer to the "impossible question".
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However, the authority says no one will be disadvantaged.
Pupils told the Herald this morning the mistake left them feeling stressed and worried throughout the test, and may have affected people's performance on other questions.
Krisztian Leyser, said he felt "a bit cheated" by the question.
"There was a lot of stress," the 18-year-old Hastings Christian School pupil said.
Others were "really confused, and some spent so long trying to figure it out they lost time on other parts of the exam".
He came across the question - which involved a table that should have added up to 100 per cent, but instead added up to 121.1 per cent - in his first paper, he said, and immediately knew it was wrong.
"I was going back over it and over it trying to find out what it was, and of course in the back of my head I'm thinking, 'I need to do this other paper as well', so it was stressful having to deal with it," he said.
Leyser tried to raise the error with the exam supervisor, but said he was dismissed as simply failing to understand the question.
"They just said, 'no one else has complained about it so surely you're just missing something'.
"So then I'm feeling a bit dumb."
He added: "I was thinking, 'what if it's just in my paper, and it's only going to be me that gets affected?'."
However, towards the end of the exam, it became clear that others were struggling too, he said.
"Quite a few people were staying in much longer than two hours and just by looking around I could see that a lot of other students were looking at the same page as me, so I had figured that there's probably something going on there," Leyser said.
The table was the first question on everyone's lips as they left the exam hall, he said.
"Everyone was freaking out about it."
He was "glad to hear" it acknowledged as a mistake, he said, but thought it could have been "easily avoided".
This morning NZQA deputy chief executive Kristine Kilkelly apologised to students, saying no student who struggled with the question would be disadvantaged.
Leyser was happy that the table would be taken into consideration during marking, but said the question was "on the back of my mind the whole paper so there's a chance that it did affect the other questions".
"Completely unfair to students" - pupil
His fears were shared by Long Bay College student Ethan Laby, who said the mistake was "completely unfair on us students".
"It is fine for NZQA to say that they will mark the paper accordingly, to ensure that the grades are fair, however they actually fail to realise the extent of the impact that having a wrong question in a test paper has on students," he said.
Students had quickly realised there was a problem with the question, he said.
"This was a very clear mistake that was picked up by everyone who stayed the whole three hours."
It was not the first exam he's sat that contained errors, he said, pointing to incorrect references, poor grammar, and "now this - a completely wrong question because someone doesn't know how to add to one".
Question was impossible to answer
MathsNZ and secondary school maths teacher Jake Wills said the mistake should not have happened. It made it impossible to answer half a question on a three-question paper.
The table error was in a probability concepts question, he said.
Students were expected to work out an answer that should have added up to 100 per cent using a table that added up to 121.1 per cent.
"It means that the entire question is not valid and you can't do that question," said Wills.
"Basically more than half of the last question was impossible."
Some senior students were so distraught it affected how they attempted the rest of the exam, he said.
One Kapiti College student posted on a maths forum: "I died because I had no idea how to finish that goddamn table and then I didn't even try with the next one because I just lost all confidence of knowing how to do it."
Wills said teachers were shocked such a serious error had managed to get through after earlier issues with exams.
"There is supposed to be a rigorous checking system in place for exams and that got through and it shouldn't have."
Kilkelly acknowledged the mistake in the paper.
"There was an error in a data table in of one of the three questions that meant students couldn't answer part of that question," she said.
"We are committed to ensuring that no student will be disadvantaged as a result."
The error slipped through despite comprehensive quality assurance processes, she said.
It would be taken into account when papers were marked.
"The examination papers will be marked as normal by the panel that has been made aware of the issue - they will take this into account when grading students work," she said.
This evening NZQA said it had received 10 complaints about the statistics exam, which it would respond to in the coming days.
It was not investigating any other serious mistakes in NCEA exams, it said.
"The only error of this significance currently under review is the Level 3 Statistics exam and we are taking it very seriously."
It's the second time this year that students have faced a controversial maths paper.
NZQA received 70 complaints after a level one algebra exam was deemed too difficult.
The Maths Common Assessment Task exam reduced students to tears. Teachers and students complained it was two curriculum levels too high and involved components not seen in previous papers.