1. Understand the Research Question:
Start by clearly stating your research question. A well-defined question will inherently point towards the variables involved. For example:
* Poorly defined: "What's the effect of exercise?" (Too broad)
* Well-defined: "What is the effect of daily 30-minute moderate-intensity exercise on blood pressure in adults aged 40-50?"
2. Identify the Independent Variable (IV):
The independent variable is the factor you *manipulate* or *observe* to see its effect. It's the presumed *cause*. In the example above, the independent variable is:
* Daily 30-minute moderate-intensity exercise. This is something the researcher can control or measure.
3. Identify the Dependent Variable (DV):
The dependent variable is the factor you *measure* to see if it's affected by the independent variable. It's the presumed *effect*. In the example:
* Blood pressure. This is what the researchers are measuring to see if it changes due to exercise.
4. Identify Control Variables (CVs):
Control variables are factors that could influence the dependent variable but are *held constant* to eliminate their effect on the outcome. They help isolate the relationship between the IV and DV. In the example, some control variables might be:
* Age (40-50 years): Restricting the study to this age range controls for age-related variations in blood pressure.
* Gender: Researchers might choose to focus on one gender to control for gender-specific differences.
* Diet: Researchers might need to standardize or control participants' diets to eliminate dietary influence on blood pressure.
* Pre-existing health conditions: Participants with certain conditions impacting blood pressure should be excluded.
5. Identify Extraneous Variables (EVs):
Extraneous variables are other variables that could potentially affect the dependent variable, but aren't being controlled or measured. Researchers aim to minimize their influence. These are often difficult to completely control for. Examples:
* Stress levels: Stress can influence blood pressure.
* Medication use: Certain medications can affect blood pressure.
6. Consider the Type of Variable:
Categorize your variables by their type:
* Categorical (Nominal or Ordinal): Represents groups or categories (e.g., gender, ethnicity, education level).
* Numerical (Interval or Ratio): Represents quantities with meaningful numerical differences (e.g., age, weight, blood pressure).
In summary: Identifying variables involves carefully analyzing your research question to determine what you're manipulating or observing (IV), what you're measuring (DV), what you're controlling (CVs), and what potentially confounding factors you need to be aware of (EVs). This clear identification is essential for designing a robust and meaningful research study.