Adevelopmental scientist is investigating impulsivity in adolescents. she wishes to determine whether impulsivity is part of a cluster of related traits. the scientist will probably conduct a:

The scientist will probably conduct a "factor analysis."

Factor analysis is a valuable tool for exploring variable connections for complex ideas, for example, financial status, dietary examples, or mental scales.  

It enables researchers to research ideas that are not effectively estimated straightforwardly by crumbling a substantial number of factors into a couple of interpretable fundamental components.  

The key idea of factor analysis is that different observed factors have comparable examples of responses since they are altogether connected with a latent (i.e. not straightforwardly estimated) variable.

d. i assume the underlined word is "role." reformat if it isn't.

explanation:

role is closest to part because when replacing words, "playing a vital decision," "playing a vital activity," and "playing a vital dollar" don't make logical sense. the only meaningful choice is "playing a vital part."

this fits one of merriam-webster's definitions of role: "a function or part performed especially in a particular operation or process."