Matching Methods to Project and Population | Interaction Design

Suitable vs Unsuitable Projects for Each Method

A standard Supervision and Tripos question type asks you to explain when a method is suitable and when it is unsuitable — not just to define the method generically, but to apply it to a specific project context.

Worked Examples: The Six Core Methods

Questionnaires

Suitable for: a large-scale redesign of a university course-feedback system — you need quantifiable, comparable data across hundreds of students, and the research questions are well-defined from prior qualitative work. The questionnaire can be deployed at scale at the summative stage.
Unsuitable for: early exploratory design of a brand-new mental-health support app, where you do not yet know what to ask about — the questions themselves would bias the research toward what the designer already thinks is important, missing completely unexpected user needs that interviews or ethnography would surface.

Interviews

Suitable for: understanding why senior citizens distrust a new banking app — rich, probing, semi-structured conversations let you follow unexpected threads and surface emotional barriers that a questionnaire’s fixed categories would miss. Used at the formative stage.
Unsuitable for: a high-frequency A/B test of button colour on a checkout page — far too slow and small-sample for a statistical comparison; a questionnaire or click-through log would be faster, cheaper, and yield actionable quantitative data.

Ethnography

Suitable for: redesigning hospital ward communication systems — a classic second-wave HCI, socio-technical problem where shift handovers involve physical artefacts (whiteboards, sticky notes, verbal reports) and the deep contextual understanding fieldwork provides is essential.
Unsuitable for: optimising the KLM timing of a keyboard shortcut — that needs controlled, quantitative measurement (Fitts’ Law modelling, lab timing), not weeks of contextual immersion.

Lab-based observation

Suitable for: comparing completion time and error rate of two checkout flows under controlled conditions — removing environmental noise lets you isolate the interface as the independent variable, enabling a t-test or sign test.
Unsuitable for: understanding how a smart-home device is actually used amid family life — the lab strips away the very context (children interrupting, different family members using the device at different times, ambient noise) that determines real-world usability. This is a low-ecological-validity mismatch.

Focus groups

Suitable for: gauging early reactions and points of disagreement about a proposed feature among diverse stakeholder groups — e.g. teachers reacting to a new classroom app, where the debate itself reveals the range of concerns.
Unsuitable for: sensitive personal topics (financial hardship, mental health, domestic abuse) where social pressure would suppress honest answers and the group setting would actively harm the quality and ethics of the research.

Card sorting

Suitable for: designing the navigation menu of a large e-commerce site — reveals how users naturally categorise thousands of products into a browsable hierarchy (Information Architecture).
Unsuitable for: evaluating a highly sequential, task-based system like an ATM withdrawal — the interaction is a fixed sequence, not a browsable hierarchy. Card sorting provides no insight into sequential task flow; a cognitive walkthrough or KLM analysis would be appropriate there.

Adapting Methods for Vulnerable or Constrained Populations

Some user groups present specific challenges that rule out certain methods:

Visually Impaired Users

For a colour-to-sound wearable device (2020 Tripos): visual questionnaires, Likert scales, and physical card sorting are problematic or impossible unless heavily adapted. Observing facial expression for engagement or frustration is not meaningful if the user cannot see and does not produce the expected expressions. Better fit: interviews, verbal think-aloud protocols, contextual inquiry, diary studies using voice recordings.

Users Under Emotional Strain

For a mindfulness app targeting anxious students (2023 Tripos): long, clinical-feeling interviews and direct observation during a panic or anxiety episode can be intrusive, stressful, or even harmful. Better fit: lightweight diary studies where the user records in their own time; validated psychometric questionnaires (standardised stress/anxiety scales); short, gentle semi-structured interviews in a comfortable setting.

Time-Pressured Expert Users

For air-traffic controllers, financial traders, or emergency dispatchers: long interviews disrupt their work and are unsafe during operations. Better fit: contextual inquiry in short bursts between shifts; structured logging/analytics of actual performance; brief post-hoc debriefs after discrete tasks.

The General Principle

When a standard method is unsuitable for a specific population, the exam answer should: (1) name the method that would normally be used, (2) explain specifically why it is unsuitable for this population — citing a concrete barrier (visual, cognitive, emotional, time-pressure), and (3) propose a modified or alternative method that addresses that barrier.

Expected Learning

For each of the six core methods, give a concrete project for which it is suitable and one for which it is unsuitable, with specific justifications.
Explain why ecological validity matters when choosing between lab and field methods.
For a given user population with specific constraints (visual impairment, emotional vulnerability, time pressure), identify which methods are unsuitable and which alternatives are appropriate.
Always use the three-step pattern: name the standard method → explain why it fails for this population → propose a concrete alternative.

Past Paper Questions

Method suitability is tested in: 2023 Q6 (mindfulness app — methods for emotionally vulnerable users), 2020 Q6 (weather app — data collection for visually impaired users), 2022 Q6 (COVID-19 app — methods under pandemic constraints). The Supervision 1 Question 2 directly tests suitable vs unsuitable projects for all six methods.