Determining Scale of Measurement 3 steps Examples Try

Determining Scale of Measurement • 3 steps • Examples • Try a few

Scales (levels) of Measurement To determine level of measurement • Step #1 Identify the Unit of Observation (obs unit) (sampling unit) – (one of something) • What you are interested on studying? • Usually the individual (participant) for psychologists • Other possible Observational units: – – – A rat A Group/team A Household A City A Country A College student

Scales (Levels) of Measurement To determine level of measurement • Step #2 Ask: “What am going to do with the Obs unit? ” – Two options: • Option A: Assign the Obs unit to a category (quality) – E. g. gender, race, social security number (unique) • Option B: Measure the Obs unit on some attribute or behavior – Intelligence, age, motivational level, number of hotdogs eaten – If “Yes” to Option A • Ask: are the categories ranked on some quality? – E. g. job class (clerical I, III) – E. g. class standing (rank in class) • If “NO”, not ranked, then level of measurement is NOMINAL • If “Yes”, categories ranked, level of measure is ORDINAL

Scales (Levels) of Measurement To determine level of measurement • If Option B: Measure Obs Unit on some attribute or behavior • Step #3 Identify Unit of Measure (Measurement Unit) – One of something (attribute or behavior) • E. g. item on a test, inventory – Ask: “Does the measure have a true zero? Usually: • Physical and behavioral ones do – E. g height, weight, number of cases sold • Psychological attributes do not – IQ, need for approval, depression level, attitude toward boss

Scales (Levels) of Measurement To determine level of measurement • If answer to “Does the measure have a true zero? ” – Is “YES”, level is Ratio – Is “No”, level is Interval • Try out a few:

What level (scale)? Number of children aboard each of 15 school buses? • Observational unit? – One school bus • Place bus in category? – No • Measurement Unit? – One student • Absolute zero? – Yes, bus could carry no students • Level of measure? – Ratio

What Level Measurement? Students Fail v. Pass • Observational unit? – One student • Place student in category? – Yes: fail or pass • Are the categories ranked on some quality? – Yes (underlying continuous variable…success in learning) • Level of measurement? – Ratio – Just kidding! – Ordinal