Answer
(a) This is an observational study as the investigator has no control. However the investigator is aware of who the people are from different groups so this is single blind
(b) This is an experimental study, since the water drinking habits of these people are those who have the motive to lose weight. So it is also single blind.
Work Step by Step
(a) Classify if the given statements are observational or experimental. They should be observational since the investigator does not have control over the treatment administered.
(b) Here the treatment is experimental as the water drinking habits of the people who want to lose weight are controlled by the people in the experiment instead of the investigator.
