In the experimental method, experimenters can confirm that an independent variable alone is the cause of the observed effects on a dependent variable by:
1. Random assignment: Participants are randomly assigned to different groups (experimental and control) to ensure that any differences in the dependent variable between groups are due to the manipulation of the independent variable and not other factors.
2. Control group: A control group is used to provide a baseline for comparison with the experimental group. The control group does not receive the manipulation of the independent variable, allowing researchers to isolate the effects of the independent variable.
3. Manipulation of the independent variable: The experimenter systematically alters the independent variable to see its effect on the dependent variable. By controlling all other variables and only manipulating the independent variable, researchers can confirm that any changes in the dependent variable are due to the manipulation.
4. Measuring and recording results: Researchers carefully measure and record the effects of the independent variable on the dependent variable in both the experimental and control groups. This helps to determine the extent to which the independent variable is causing the observed effects on the dependent variable.
5. Replication: Conducting the experiment multiple times and obtaining similar results strengthens the researchers' confidence that the independent variable is causing the observed effects on the dependent variable. This helps to establish the reliability and validity of the findings.
By employing these methods, experimenters can confidently establish a cause-and-effect relationship between the independent variable and the dependent variable in an experiment.