Answer :
Final answer:
Third variables play a critical role in nonexperimental methods by potentially affecting the relationship between variables and are controlled for to improve the study's validity.
Explanation:
Third variables are variables not part of the research hypothesis but can cause a correlation between predictor and outcome variables. They introduce alternative explanations, reducing study validity, and are often controlled for as control variables in data analysis to enhance research quality. In the context of nonexperimental methods, they are crucial in identifying and addressing confounding factors.
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