Analyse an area of computer science

Digital Technologies | Level 3 | AS 91908 (3.9) | 3 Credits 

*** In 2025 this external will be an Online Examination held on WEDNESDAY 12th NOVEMBER - PM ***

This exam asks students to analyse a specific area of computer science. Students need to go beyond just describing the topic, they need to explain how it works, explore real-world examples, discuss its challenges, and evaluate its impact from different perspectives.

This is a chance to show not just what they know, but how well you can think critically about a complex computer science idea.

Every year, THREE topics are named in the NZQA Assessment Specifications for Teachers and Students to focus on. In the exam students choose to answer questions for ONE topic only.

In 2025 the THREE topics are: Complexity and tractability, Computer vision, Computer graphics

From the NZQA 91908 Assessment Specifications 2025:

Candidates will be required to respond in short and / or extended answers (800–1500 words in total) to questions relating to their choice of ONE of the following computer science concepts: 

• Complexity and tractability

• Computer vision

• Computer graphics. 

For Complexity and tractability, questions may cover: polynomial and non-polynomial time complexity, Big O notations O(1), O(log n), O(n) , O(n^k), O(2^n), O(n!), and best-case, worst-case, and average-case time complexity, complexity classes (P, NP, NP-complete), solving complex problems (approximation algorithms / heuristics), algorithm design and optimisation, optimal solutions (Travelling Salesman / knapsack, etc.).  

For computer vision, questions may cover: noise, thresholding, edge detection, image processing for computer vision, applications in fields of obstacle detection (e.g. Lidar and stereo vision), feature extraction (e.g. Viola Jones, Haar-like features) and medical detection, and the application of techniques to medical diagnosis (e.g. convolutional neural networks, decision trees, and random forests). 

For computer graphics, questions may cover: bitmap and vector graphics, matrices and transformations, line and circle algorithms (e.g. Bresenham's line algorithm, midpoint circle algorithm), image rendering (raytracing vs rasterisation), texture mapping, lighting, and lighting effects and reflections. 

Special notes: 

• Teachers are encouraged to help their students to develop answering techniques to ensure that they are able to respond clearly and concisely within the total recommended word limit. Responses that exceed this may not be considered for assessment past the 1500-word limit. 

• Teachers are strongly encouraged to prepare students to be able to apply their understanding of computer science to unfamiliar contexts.  

• Teachers should prepare students to identify and articulate instances where overlap with various areas of computer science occurs, e.g. with artificial intelligence.  

Why you should look at the Assessment Report

Every year an assessment report is released to support teachers and students understand how the exam was marked. There can be some specific detail which is worth reading through to help support students understand the grade recieved. 

We recommend reading through the whole report yourself. These are found under the different years below but here are some of the key points:

• Candidates’ knowledge and understanding of content, skills, and complexities must be at Level 8 of the New Zealand Curriculum. 

• Candidates displayed a good grasp of computer science concepts, consistent with Level 8 of the New Zealand Curriculum. 

• Candidate responses that were able to showcase a thorough understanding of the topic by discussing it with both depth and breadth, going beyond what is covered in available resources, achieved at higher levels. 

• Overall, successful candidates differentiated themselves by the depth of their technical understanding, the relevance and application of examples, the originality of their connections, and their ability to critically analyse and predict future developments in areas of computer science. 

• Candidates who made minor errors in their submissions were not penalised if they demonstrated sufficient understanding throughout the submission. However, candidates who made errors and failed to show comprehensive understanding in their detailed responses often struggled to achieve.  

Assessment Reports, Assessment Schedules, Exemplars (and the blank exam)

In the drop downs below you will find the Assessment Report, the Assessment Schedule and any exemplars NZQA provided

Note: Perviously to this year the 91908 external was a DCAT.