Overview
This lecture introduces the different types of variables used in quantitative research, including how to classify and identify them in practical scenarios.
Understanding Variables
- A variable is a measurable characteristic that can change or have different values.
- Variables can hold numerical or categorical (descriptive) values.
- A variable is only relevant if it varies within the research context (e.g., gender is not a variable in an all-girls school).
Classification of Variables
- Variables are classified as continuous or discrete.
- Continuous variables can take any value within a range, including fractions (e.g., age, height, temperature).
- Discrete variables have a limited number of separate, distinct values and cannot be subdivided (e.g., number of children, blood group, sex).
Types of Continuous Variables
- Interval variables have meaningful differences between values, but no true zero (e.g., temperature in Celsius).
- Ratio variables have all the properties of interval variables, plus a true zero point (e.g., height, weight, distance).
Types of Discrete Variables
- Nominal variables are categories without any order or ranking (e.g., type of business, religion).
- Ordinal variables are categories with a meaningful order or ranking (e.g., levels of satisfaction, educational attainment).
Independent and Dependent Variables
- Independent variable: the "cause" variable that brings about change (e.g., number of times you walk per week).
- Dependent variable: the "effect" or outcome variable that changes in response (e.g., occurrence of diseases).
Example Scenarios
- In testing detergent, the independent variable is the brand of detergent; the dependent variable is stain visibility.
- For studying walking and health, the independent variable is frequency of walking; the dependent variable is occurrence of diseases.
Key Terms & Definitions
- Variable — a measurable characteristic that can change within a study.
- Continuous Variable — can take an infinite range of values, including fractions.
- Discrete Variable — limited set of separate, distinct values.
- Interval Variable — differences between values are meaningful; no true zero.
- Ratio Variable — like interval, but has a true zero.
- Nominal Variable — categories without order.
- Ordinal Variable — categories with a logical order.
- Independent Variable — the variable manipulated or classified as the cause.
- Dependent Variable — the outcome affected by the independent variable.
Action Items / Next Steps
- Review examples of identifying variable types in real-world scenarios.
- Practice classifying variables in sample research questions.