Variables

Core Concepts

1. Measurement realism

   • Every variable has a real, absolute score (T)

   • Studies try to most accurately represent the true value

2. Operationalization

   • Specific representation of what is being measured and how

Variable Types

1. Discrete variables

1. • Measured by distinct categories

   • Do not necessarily exist on a continuum

     1. Nominal – the least concrete of the categorical variables. Essentially you have arbitrarily named categories with differences that are not equal. Examples include:

        • Smoker: Yes, No

        • Vaccinations: Yes, No, Unsure

     2. Ordinal- the second worst (or third best, if you’re an optimist), ordinal variables can be ordered and are definitely related, but the differences between them are not necessarily equal. Examples include:

        • Personal Health Status: Poor, Fair, Good, Very Good, Excellent

        • Use in the last 30 days: Never, Not in last 30 days, 1-2 days, 3-5 days, 6-10 days, 11-19 days, 20-29 days, All 30

     3. Interval – there is definite, equal, significant difference between each of the variables. Examples include:

        • Body Mass Index

        • Annual income

     4. Ratio – the best of the discrete variables. There are significant, defined, equal intervals and, and this is key, there is an absolute zero. Examples include:

        • Number of drinks

        • Number of sexual partners

        • BAC

2. Continuous Variables

   • Infinite options that can exist on a number line

   • Ex: age, years in school, hours working, or healthcare visits

3. Interpretation

   • Continuous and discrete variables can overlap but determination is based on operationalization