What is psychometrics?
The science concerned with evaluating the attributes of psychological tests. It’s relevant to all aspects of psyc - research and practice. It focuses on 2 major attributes, reliability and validity.
Psychological measurement plays 3 critical roles. What are these?
- Decide which test to use in a given situation
- Interpret the scores from a test in a given situation.
- Possibly create hour own test for a given situation.
Deciding on a test depends on understanding the application of concepts such as:
- reliability
- validity
- norms - relative to everyone else
- test discrimination - tests discriminate between people e.g. Spatial attention questions favour men on IQ test
In psychology, the attribute of interest is often not observable directly.
Instead Psychologists rely upon a collection of several overt behaviours as indirect indicators of the attribute of interest.
What is working memory?
WM is the capacity to maintain and manipulate information in STM.
How do psychologists measure unobservable attributes?
With a variety of tests (operational definitions). Need to try to get at the unobservable psychological attribute from more than 1 angle.
How is the WM attribute measured?
With 4 tests thought to reflect WM.
What is a psychological construct?
An unobservable hypothetical entity that is used to represent a pattern of psychologically related phenomena. E.g. WM, intelligence
It’s a more sophisticated psychometric term for ‘psychological attribute’.
Psychological constructs are abstract.
The role of theory - why must a construct be clearly defined?
- A clearly defined construct dismisses obvious irrelevant indicators of the construct of interest.
- E.g. Running speed is obviously irrelevant to WM capacity.
- Tests or indicators used to represent a construct should be linker theoretically to the definition of the construct.
- There is no empirical or statistical test to determine this.
- It’s purely a qualitative exercise
Operational Definitions
- Psychological constructs are not observable directly
- Arguably, many of them can be measured indirectly with tests.
- These tests are considered operationalizations of the construct.
- constructs tend to be both abstract and general.
- in practice, we have to move from the general to the more specific if we are ever going to measure it.
- people devise tests consistent with the definition of the construct in the hopes of capturing its essence.
- However, no test actually represents the construct perfectly.
What is a psychological test?
A systematic procedure for comparing the behaviour of 2 or more people. There are 3 components to this definition:
- Tests involve behavioural samples of some kind - multiple items
- The behavioural samples must be collected in some systematic way. (Everyone who completes it does so in the same way and under the same conditions)
- The purpose of tests is to compare behaviours of 2 or more people.
In psychology, what does the word ‘test’ mean?
A procedure designed to collect data from people in a systematic way.
What is the purpose of psychological testing?
- The main purpose is to compare the cognition/behaviour of different people.
- This is known as ‘inter-individual differences’
- Tests can also be used to measure changes in the behaviour of people across time.
- This is known as measuring ‘intra-individual differences’
- The purpose of measurement in psychology is to quantify inter-individual and/or intra-individual differences.
Types of test
- Many tests have been published
- They vary along 5 dimensions:
1. Content (e.g. Skill, personality, attitudes)
2. Types of responses (e.g. Multiple-choice, open-ended)
3. Administration procedure (e.g. Individual vs. group)
4. Intended purpose (criterion vs. norm referenced)
5. Time constraints (speed vs. power)
Criterion referenced tests
- used in contexts where a decision is made about someone’s skill level.
- Involve a cut-off score that specifies whether someone has achieved a sufficient level of the skill or capacity.
- Are typically used in personnel selection contexts.
- E.g. Candidates must demonstrate a minimum capacity to type 60 words per minute.
Norm referenced tests
- Involve comparing a person’s score with a reference sample.
- A reference sample is considered to be representative of the population of interest.
- A person’s score is compared against the average of what you would expect from all people in the population of interest.
- In some cases, a norm referenced test may be used in a criterion referenced way.
- E.g. You may need to score at the 75th percentile of a test in order to get accepted into a program.
