Understanding Research Methods and Their Requirements

Research methods are systematic approaches used to collect and analyze information to answer research questions or test hypotheses. Different research methods have distinct characteristics and requirements, especially concerning how variables are handled and participants are selected.

The question asks to identify the research method where manipulation and control of variables, and randomization of sample are two of the basic requirements.

Analysing the Research Methods Options

Let's look at each option provided:

• Ex-post facto research: This method studies potential cause-and-effect relationships after the fact. The researcher does not manipulate the independent variable; it has already occurred. Control over extraneous variables is limited, and randomization of participants to different conditions is usually not possible.
• Descriptive research: This method aims to describe the characteristics of a population or phenomenon. It focuses on answering questions like "what," "where," "when," and "how." There is no manipulation of variables in descriptive research.
• Case study research: This involves an in-depth, detailed examination of a single case or a small number of cases. While it provides rich information, it does not typically involve manipulation of variables or randomization of a large sample in the way required by the question.
• Experimental research: This method is designed to determine cause-and-effect relationships. It involves the researcher deliberately manipulating an independent variable (or variables) and observing the effect on a dependent variable. Control over extraneous variables is crucial to ensure that the manipulated variable is truly causing the observed effect. Randomization of participants to different groups (like experimental and control groups) is a key technique used in experimental research to ensure that the groups are equivalent at the start of the experiment, thereby reducing the influence of confounding variables and making the results more generalizable and internally valid.

Key Requirements: Manipulation, Control, and Randomization

Based on the analysis, let's specifically consider the requirements mentioned in the question:

• Manipulation of variables: This refers to the researcher actively changing the level of the independent variable to see its effect.
• Control of variables: This involves minimizing the influence of extraneous variables that could affect the relationship between the independent and dependent variables.
• Randomization of sample: This often involves randomly selecting participants from a population or randomly assigning selected participants to different experimental conditions.

Experimental research is the method that fundamentally requires the researcher to manipulate an independent variable and maintain significant control over other variables. Random assignment of participants to experimental conditions is a cornerstone technique in experimental design to enhance the internal validity by creating comparable groups.

Comparing Research Methods Based on Requirements

As the table shows, Experimental research is the only method among the options that fundamentally requires the manipulation and control of variables and prominently uses randomization (specifically, random assignment) as a basic requirement for strong design.

Conclusion on Basic Requirements in Research

Therefore, the research method that has manipulation and control of variables, and randomization of sample as two of its basic requirements is Experimental research.

Revision Table: Key Features of Research Methods

Additional Information on Experimental Research

Experimental research is considered the gold standard for establishing causal relationships because of the control and manipulation involved. Key concepts include:

• Independent Variable (IV): The variable manipulated by the researcher.
• Dependent Variable (DV): The variable measured to see the effect of the IV.
• Experimental Group: Receives the treatment or manipulation of the IV.
• Control Group: Does not receive the treatment or receives a standard/placebo treatment, serving as a baseline for comparison.
• Random Assignment: Assigning participants to experimental or control groups randomly ensures groups are comparable before the manipulation, distributing potential confounding variables evenly.
• Extraneous Variables: Variables other than the IV that could affect the DV. Researchers try to control these through design, procedures, and statistical techniques.

The combination of manipulation, control, and randomization strengthens the internal validity of an experiment, making it more likely that the observed effect on the dependent variable is indeed caused by the independent variable.