Answer :
Final answer:
A correlational study is used to investigate the relationship between caffeine consumption and sleep quality through questionnaires, without manipulating variables.
Explanation:
Correlational study is the method employed when investigating the relationship between caffeine consumption and sleep quality through questionnaires. In this study, data is collected from participants to identify if there is a correlation between the two factors without any manipulation by the researcher.
Observational studies are typically easier to carry out and the subjects are not intervened with, making it suitable for ethical reasons. This method allows for the gathering of data from participants through measurements or answers to questions without altering variables.
Learn more about Correlational study here:
https://brainly.com/question/30357886
