Research methods 22 | Levels of measurement: nominal, ordinal and interval. Flashcards
What are the three main levels of measurement in psychology?
Nominal, Ordinal, Interval
What is nominal data?
Data where numbers represent categories (e.g., pet types, country of origin). No mathematical relationships.
What is a key characteristic of nominal data?
Categories are distinct; no order or numerical meaning (e.g., ‘dog’ ≠ 2 × ‘cat’).
What is ordinal data?
Data that can be ranked (e.g., race positions, Likert scales), but intervals between ranks are unequal.
Why can’t ordinal data show exact differences?
The gap between 1st & 2nd may not equal 4th & 5th (e.g., happiness scales).
What is interval data?
Data with equal intervals between measurements (e.g., temperature °C, reaction time in ms).
How does interval data differ from ordinal?
Interval allows precise comparisons (e.g., 4mm is double 2mm); ordinal only ranks.
What is ratio data?
Interval data with a true zero (e.g., length in mm, time in sec). Temperature °C is not ratio (can be negative).
Example of nominal data in a race:
Runners’ countries (e.g., 2 from USA, 1 from Jamaica).
Example of ordinal data in a race:
Finishing order (1st, 2nd, 3rd).
Example of interval data in a race:
Exact finish times (e.g., Bolt won by 0.2 sec).
Can you convert interval data to ordinal?
Yes (e.g., convert race times to ranks: 1st, 2nd, 3rd).
Can you convert nominal data to interval?
No—nominal lacks numerical order/precision.
Which level of measurement is most precise?
Interval (and ratio).
Which level is least precise?
Nominal (only categories).
