If a researcher wishes to study the relationship between self-esteem and level of intelligence, then gathering data about participants’ eye color would be __________.

The study is about the relationship between self-esteem and intelligence, so the researcher should collect information relevant to those variables. Eye color is not ordinarily related to either variable and would not help answer the research question. Therefore, gathering eye-color data is unnecessary because it does not relate to the topic of the study.

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