Final answer:
The number of smiles that occurred during the 15-minute period when measuring happiness is the dependent variable, as it is what the researcher measures in response to the manipulation of another variable.
Step-by-step explanation:
In the context of counting participants' smiles during a 15-minute period to measure happiness, the number of smiles constitutes the dependent variable. The dependent variable is the observed outcome that researchers measure in response to the manipulation of the independent variable. In this scenario, the independent variable is the variable manipulated by the researcher, which could be the introduction of a comedy clip.
The researcher controls the presentation of the comedy clip to examine its impact on participants' happiness, operationalized as the number of smiles. The dependent variable, being the observed behavior (smiles), is then analyzed statistically to discern the effect of the manipulated independent variable (comedy clip) on the participants' happiness. This experimental design allows for a systematic investigation into the relationship between the independent variable and the resulting behavior, providing insights into the factors influencing happiness.