Practical Research Lesson 3: Variables in Studies

Study Notes

Variable Definition: A variable is any element that has varying quantities or qualities.
Dependent Variables: Metrics that are affected by changes in independent variables. Example: growth of tomato seedlings and fruit yield.
Independent Variables: Factors manipulated by the researcher. Example: amount of sunlight, water, soil type, and nutrients affecting tomato growth.
Extraneous Variables: Uncontrolled factors that may influence the dependent variable such as pests and environmental stressors during an experiment.
Confounding Variables: When an extraneous variable significantly affects the outcome, making it difficult to isolate the effects of independent variables.

Controlling extraneous variables is vital for maintaining the internal validity of an experiment.
Methods of control include holding variables constant or distributing their effects equally across treatments.

Quantitative Variables: Numerical variables that can be measured. They are categorized into discrete and continuous.
- Discrete Variables: Countable whole numbers that do not include negative values, e.g., number of students in a class.
- Continuous Variables: Values that can be fractional, encompassing both positive and negative numbers, e.g., height or temperature measurements.

Also known as categorical variables, these are non-numerical and represent descriptions or categories.
Types of qualitative variables include:
- Dichotomous Variables: Two distinct categories, e.g., yes or no responses in surveys.
- Nominal Variables: Define groups without any inherent ranking, e.g., jersey numbers of athletes or blood types.
- Ordinal Variables: Ranked categories that allow for ordering but not specific distances between ranks, e.g., academic honors or survey response scales.

Variables can be categorized into quantitative (numerical) and qualitative (descriptive).
Each type has distinct characteristics and appropriate applications in research contexts.
Understanding these classifications helps in designing and interpreting research methodologies effectively.