L1: Intro to psychometrics and scaling

Question 1

What is Psychometrics and its 3 critical roles

Answer 1

The science concerned with evaluating the attributes of psychological tests: reliability and validity

1. Decide which test to use in a given situation.
2. Interpret the score from a test in a given situation.
3. Possibly create your own test for a given situation.

Question 2

what is a psychological construct? How do we assess psychological constructs and why is it hard?

Answer 2

• abstract entity which represents a pattern of psychologically related phenomena
• hard because constructs are not observable directly - must be measured indirectly through inference of behaviours (operationalisations) that are believed to represent the construct of interest

Question 3

What is a psychological test, 3 components to this definition?
what is the purpose of psychological testing?

Answer 3

a systematic procedure for comparing the behaviour of two or more people:
1. tests involve behavioural samples
2. samples must be collected in systematic way
3. purpose of this is to compare behaviours or two+ people

Measuring inter-individual differences:
- to compare the cognition behaviour of different people
Measure Intra-individual differences:
- changes in the same people over time

Question 4

5 dimensions in which tests can vary

Answer 4

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)

Question 5

criterion vs norm-referenced test

Answer 5

Criterion
- assessing the skill level
- there is a cut off score which indicates whether they’ve achieved desired skill
eg personnel selection tests for job interviews etc driving test

Norm
- compares a person’s score with a reference sample of the population of interest
- the score is compared against the average of what you would expect from all people in the population of interest
eg percentiles
eg criterion norm reference is you need 75 percentile to get into honours

Question 6

scaling

Answer 6

the way in which numerical values are assigned to psychological attributes

Question 7

3 properties of psychological measurement

Answer 7

1) Properties of identity.
- Categories that differentiate psychological features.
- differences in kind/qualitative/no continuum.
- mutually exclusive eg introvert cannot also be extrovert
- exhaustive eg all fit into one or the other
- all people classified in the category are identical in terms of the attribute of interest
- eg either has ADHD or doesn’t

2) Properties of order
- ranking
- property of order is informative,
- it’s clear systematic guidelines spell out the connection between labels (so they could also be letters)
- eg rank students scoring highest to lowest for 1 to 10 or A to J

3) Properties of quantity
- provides information about the magnitude of differences
- 1 is the most basic unit and considered real eg defines 1 on a certain scale
- all other numbers are multiples or fractions of 1
- indicates the amount of something.
- allows meaningful comparisons

4) the number 0
- May / may not imply total absence of an attribute
- zero = absolute = total absence of an attribute, can be interpreted
- OR zero = relative (arbitrary), = no clear meaning e.g. Fahrenheit scale, is not the total absence of heat
- Percentile score can indicate only 1% of the population scored less than they did, hence can still have ‘adequate’ skills on the psychological attribute of interest

Question 8

counting and additivity
measurement

Answer 8

assumption of counting is additivity:
- Additivity: the unit size of a measurement does not change as the units are being counted.
- When additivity is perfectly satisfied, we refer to the condition as ‘conjoint measurement’.
- additivity is hard to satisfy in psychology and rarely is eg exam questions vary in difficulty. in this case, you must acknowledge this as a limitation of your study
- counting is not an assumption for measuring eg counting pebbles on a sidewalk is not measuring.

Stevens 1946 MEASUREMENT = the assignment of numerals to objects/ events according to rules or observations of behaviours
there are 4 LOM
- Nominal
- Ordinal
- Interval
- Ratio

Question 9

nominal scales

Answer 9

• It is the most fundamental level of measurement.
• Numbers have been assigned to categories with no meaningful order
• Truly nominal scales do not have any apparent sequential order.
• only measure properties of identity
• for example male, female, non-binary
• state you live in WA, NSW

Question 10

ordinal scales

Answer 10

• reflect qualitative differences in amounts of an attribute to symbols or numerals
• measure properties of order and identity
• for example ranks and percentiles

Question 11

interval scales

Answer 11

• there is a constant distance between each of the units with no meaningful 0
• for example degrees Celsius or
• measures properties of identity, order, quantity

Question 12

Ratio scales

Answer 12

• there is a constant distance between each of the units but it has a meaningful 0.
• identity, order, quantity, meaningful 0
• E.g. something has 37% more than something else, or score 50 represent twice as much as score of 25

Question 13

PSYCHOLOGICAL Assessment vs PSYCHOMETRIC

Answer 13

Pysch assessment = about the diff types of test that have been published how to administer them + interpret the scores

Psychometrics = science concerned with EVALUATING the attributes of psychological test
o Relevant to type of data generated by the application of psychological tests
o The reliability of data for psychological tests (PT)
o The Validity of data obtained from PT