In one line: Before you can study "stress" or "memory", you have to decide exactly how you will measure it.
Psychology studies things that cannot be seen directly: stress, memory, attention, happiness. An idea like this is called a construct.
The key move is operationalisation. "Stress" becomes the score on a 20-question stress questionnaire. "Memory" becomes the number of words recalled in two minutes. The idea can now be counted.
Remember: Define it, then count it.
A score for stress is a measure of stress. It is not stress itself.
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Key idea: Behaviour can be recorded as numbers or as descriptions, and gathered by asking people or by watching them.
Quantitative and qualitative data
| Quantitative | Qualitative | |
|---|---|---|
| What it gives | Numbers: scores, counts, times | Descriptions: words, themes, meanings |
| Example | Number of words recalled | What a person says memory feels like |
| Strength | Easy to compare and analyse | Rich detail and context |
Two ways to gather it
Self-report
Ask people directly: questionnaires, rating scales, interviews.
Good for feelings. But people may not be honest or accurate.
Observation
Watch and record what people do.
Good for real behaviour. But thoughts and feelings cannot be seen.
Ask them · Watch them
Take a study of exam stress. Students rate their stress from 1 to 10, which is quantitative self-report. A researcher also counts how often each student fidgets during a mock exam, which is observation. Two measures of the same idea.
More than one measure: If a questionnaire and an observation point the same way, the finding can be trusted more.
Relying on a single measure is a weakness worth pointing out.
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Key idea: Some measures record the behaviour itself. Others record a sign of it, or a memory of it.
Direct measure
- Records the behaviour itself
- Words recalled, minutes on task
- Little guessing needed
Indirect measure
- Records a sign of something hidden
- Heart rate as a sign of stress
- A brain scan as a sign of thinking
Timing matters too. A study can ask people to look back and report what happened (a retrospective approach), or record things as they happen and follow people forward (a prospective approach).
Looking back is quick, but memory is not a recording. People forget, and they tidy up the past.
Exam tip: Ask of any measure: is it what people said (self-reported data) or what was recorded (empirical data)?
And was it recorded at the time, or remembered later?
Key idea: Even careful measurement can mislead. A study can find something that is not there, or miss something that is.
A false alarm
- The study finds an effect that is not real
- It happened by chance in this sample
- Called a type I error
A miss
- The study finds nothing, but the effect is real
- Often because the sample was small
- Called a type II error
A result is called statistically significant when it is unlikely to be chance. Unlikely is not impossible: when there is really nothing to find, about one study in twenty still comes out significant by luck.
That is why one study is never the last word. When other researchers repeat it and find the same, a false alarm becomes very unlikely.
Remember: Type I: a false alarm. Type II: a miss.
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How this is asked: Measurement is one of the four concepts in the 15-mark question on a study you are given.
It is also asked in 4 marks about your own class practical.
Your class practicals
- Your class runs four small studies of its own, called class practicals.
- They are an experiment, an interview, an observation and a survey.
- Paper 2 asks about the ones your class ran.
- Keep a short note of each: aim, what you did, who took part, what you found, and the ethics.
The pattern
- Say how each variable was operationalised: what exactly was recorded?
- Is it self-reported or recorded? Direct or indirect?
- Was it measured at the time, or remembered later?
- Say what the measure could be picking up other than the idea.
- Link to a second concept, then conclude.
The trap: "the measure was bad": Say what the measure records and what it misses.
"A rating from 1 to 5, given a month later" is a criticism. "Bad measure" is not.
Discuss the following study with reference to two or more of the following concepts: bias, causality, measurement and/or responsibility.
A researcher wanted to find out whether students who are more stressed before exams sleep less. She gave 120 students a questionnaire one month after their exams. It asked them to rate how stressed they had been in exam week on a scale from 1 to 5, and to estimate how many hours they had slept each night that week. Students who gave higher stress ratings reported fewer hours of sleep. She concluded that exam stress reduces sleep.
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