Apsychiatrist studying the affects of healthy eating habits on mood improvement. he identifies 25 people who eat healthy food and 25 who do not. each other 50 people is given a questionnaire design to determine their mood. none of the 50 people participated in the study knew they were part of the study. which statement is true? a this is a random mise comparative experiment be this is a double blind study see this is an observational study d this is matched pairs design