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Reliability, Validity and Questionnaire Design

What makes data trustworthy? Learn the exam definitions of reliability and validity, and how to design a questionnaire that collects fair, useful data.

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What you'll cover

What makes data trustworthy? 📊

Good statistics need good data. Two ideas measure data quality: **reliability** and **validity**. This module covers both, plus how to design a **questionnaire** that collects fair, useful data.

Key terms 📖

Learn these definitions word for word:

Match each term to its definition

  • Reliability
  • Validity
  • Pilot
  • Leading question
  • The extent to which repeated measurements yield similar results
  • The extent to which a test measures what was intended
  • A small trial run before the main survey
  • A question that pushes towards a particular answer

Define reliability

What does reliability mean in statistics?

  • The extent to which repeated measurements yield similar results
  • The extent to which a test measures what was intended
  • The number of people in a sample
  • The cost of running a survey

Designing a good questionnaire 📝

A good questionnaire collects trustworthy data. Avoid **leading questions** that push an answer, and **biased or emotive** wording. Use **closed** questions for quick, comparable data and **open** questions for detail. Always run a **pilot** first to catch problems, and keep it short so people finish it.

Spot the poor questions

Select the TWO questions that are leading or biased.

  • "Do you agree our wonderful park deserves more funding?"
  • "How many hours of television do you watch per day?"
  • "Most people recycle. Do you recycle too?"
  • "Which age group are you in?"

Match each feature to the practice it shows

  • A leading question
  • Running a pilot first
  • A closed question with set options
  • Emotive, biased wording
  • Poor practice: it pushes an answer
  • Good practice: it tests the questions first
  • Good practice: it gives quick, comparable data
  • Poor practice: it sways the respondent

Open or closed?

Which of these is a closed question?

  • "Which of these do you prefer: A, B or C?"
  • "What do you think about the new park?"
  • "Tell us your views on recycling."
  • "Describe your journey to school."

Running a questionnaire

An interactive activity.

Data-quality frame

A measurement is _____ if repeating it gives similar results. A test is _____ if it measures what was intended. Before a main survey, researchers run a _____ to find problems. A _____ question should be reworded because it pushes the respondent towards an answer.

reliable valid pilot leading random biased census closed

Reliable is not the same as valid ⚖️

The two ideas are different. A measurement can be **reliable but not valid**: a scale that always reads two kilograms too heavy is **consistent** (reliable) but **wrong** (not valid). Good data needs **both**: consistent results, and measuring the thing you actually intended.

Reliability or validity?

An interactive activity.

Fix a poor question

An interactive activity.