https://www.nzqa.govt.nz/assets/qualifications-and-standards/qualifications/ncea/NCEA-subject-resources/Mathematics/L3-Stats-Formulae-2013.pdf
Click on the link above to see the formulae sheet that you will get with your External
Here is the link for the exemplars from 2017 and the years before...click on the year...at the bottom you will see the schedules which will have the answers: