Select the correct definition of an observational study from the choices below. A study where subjects are selected based on convenience to the researcher. A study that rejects or fails to reject a statistical hypothesis about a population parameter. A study where neither the subjects nor the researchers know what treatments are being administered to which subjects. A study where researchers manipulate variables and impose treatments on the subjects in the study, then measure and record the responses of the subjects. A study where researchers measure and record data about the subjects in the study, but do not apply any treatments to the subjects or manipulate any variables.