Years 11–13Mathematics and StatisticsEvidence Lock + Decision Vignette
Locking evidence before the numbers do the talking
Making statistical decision-making visible before the investigation begins
The condition
Students preparing statistical investigations at NCEA level can now arrive at the analysis stage with a question framed, a dataset selected, and an approach outlined — none of which they constructed themselves. The result is a student who can submit a technically credible investigation without having made a single genuine statistical decision. This is the condition Evidence Lock is designed to address.
The move — Evidence Lock + Decision Vignette
Evidence Lock establishes an approved evidence set before any analysis begins. The Decision Vignette creates a secure in-class evidence point that confirms the student owns the decisions behind the work.
Before any analysis or write-up, students select three anchors from their dataset or inquiry context: a key variable they have chosen to focus on, a data feature they identified as significant, and a limit or uncertainty in the data they are working with.
For each anchor, students write one sentence explaining why it matters for their investigation. These are the lock. No analysis or drafting proceeds until the teacher has seen them.
Students complete the investigation using the locked anchors as the spine. AI may assist with calculations, graphs, or structure, but any claim that goes beyond what the locked evidence supports must be flagged by the student.
During the task, the teacher conducts a brief Decision Vignette with each student — 60 to 90 seconds: one statistical decision they made, one piece of evidence they used to make it, one thing they are uncertain about in their analysis.
The three anchor sentences and a brief teacher note from the vignette are collected as part of the assessment record.
What the student produces
Three written anchor sentences justifying evidence selections, submitted before analysis begins, and a vignette record confirming the student can articulate a key decision and a genuine uncertainty. The investigation itself travels with this evidence trail. Teachers can assess the quality of statistical reasoning from the anchor sentences and the vignette, independent of how fluent the written analysis reads.
Why it holds up
Statistical investigations require judgements about variables, methods, and data limits. These are the moves that cannot be outsourced because they depend on the student's understanding of their specific context. Evidence Lock places the first assessable commitment at the point before any output is produced. The Decision Vignette creates a second, independent evidence point under classroom conditions.
Teacher judgement note
For NCEA internal assessment, check current NZQA conditions for your specific standard before deciding how to incorporate the vignette record into formal evidence. The vignette is designed as a teaching and authenticity monitoring tool; its status as summative evidence will depend on your assessment context.
Governance reminder
Discuss with your HOD how the Evidence Lock anchors and vignette notes function as an authenticity record for NCEA moderation purposes. When your faculty uses consistent lock expectations across statistical investigations, students engage with variable selection and data interpretation more deliberately before reaching for a tool.
