Final answer:
An observational study observes and measures variables without trying to influence the responses, useful when experiments are unfeasible or unethical.
Step-by-step explanation:
The type of study that observes individuals, measures variables of interest, and does not attempt to influence responses is called an observational study. Unlike experimental studies, where the researcher manipulates one variable to determine its effect on another variable, observational studies simply record what is occurring without intervention. This type of study can be useful in cases where it is unethical or unfeasible to conduct an experiment. A classic example of an observational study is taking a political poll to understand voter preferences without trying to influence their choices.