CONCEPT TO BE INCLUDED Variable Value

Variables as ‘constructions’

aim Variables are ‘constructed’ by researchers

Example: AGE

Theoretical variable(s) Research questions Research questions are about theoretical variables describing units Theoretical variable(s) Unit (s) Data

Variables (DEF.) A ‘variable’ is a complete and mutually exclusive set of attributes or values. Example: Age (of a human being) has values: 0 to120. Every unit (human being) has an age (complete) + you cannot be both 10 and 20 (mutually exclusive)

Attributes or Values? The words ‘values’ and ‘attributes’ refer to the same thing, however ‘values’ is more often used to refer to ‘numerical’ attributes (age or weight) ‘attributes’ is more often used to refer to ‘non-numerical’ attributes (colors, religions) In SPSS and similar programs, even attributes like colors have ‘numbers’.

Five levels of measurement Dichotomy / Dummy SPSS terminology: Dichotomy / Dummy Nominal Ordinal Interval Ratio NOMINAL ORDINAL SCALE

Ratio If the values can be ordered, the distance between the values is known, and there is a meaningful ‘zero’ point, the variable is called a ‘ratio’ variable Example: Age of a person (Trick: you can say ‘twice as old’: 30 is twice as old as 15)

Age as a ‘ratio scale’ Age of a person Measured or defined in: YEARS? MONTHS? DAYS? …

Ordinal Example: 0-18 19-35 36-64 65-older If the values can be ordered, but the distance between the values is unknown, the variable is called ‘ordinal’ Age in categories Example: 0-18 19-35 36-64 65-older What do we know about the difference between someone in 1 and someone in 3? Or even two people within 1?

Dichotomy If a variable has two attributes only: dichotomy. Age 0-18 Age over 18 What do we know about the difference between someone in 1 and someone in 2?

WHICH CONCEPTUALIZATION IS ‘BEST’? Is depends on what you expect: Babies: ratio variable in days, weeks or months Participation in elections: ordinal variable Effects of being allowed to drive a car: dichotomy

THIS MICROLECTURE Variables are ‘constructed’ by researchers How they are constructed depends on The research question What you ‘think’ (theory)