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Determining Scale of Measurement. 3 steps Examples Try a few. Scales (levels) of Measurement To determine level of measurement. Step #1Identify the Unit of Observation (obs unit) (sampling unit) (one of something) What you are interested on studying?
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Determining Scale of Measurement • 3 steps • Examples • Try a few
Scales (levels) of Measurement To determine level of measurement • Step #1Identify 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 MeasurementTo 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, II, 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 MeasurementTo 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 MeasurementTo 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