Question

there is an experiment. Does diet affect blood pressure? All subjects go through all three treatments. First, they eat a diet with a lot of salt. Their blood pressure is measured. Second, they eat a diet with a lot of sugar. Their blood pressure is measured again. Third, they eat a diet with a lot of protein. Their blood pressure is measured a third time. Describe exactly what an order effect may look like.

Why are carry over effects problematic. Explain using the experiment in question Explain how a specific carry-over effect that you need to describe would affect the result.

Answer 1

An order Effect may look like as follows:

Treatment 1: Salt

Treatment 2: Salt + Sugar (because of carry over of Salt of Treatment 1)

Treatment 3: Salt + Sugar + Protein (Because of carry over of Salt in Treatment 1 and Sugar in Treatment 2)

Carry over effects are problematic in Within - Subjects experiment because an effect of being tested in one condition on participants' behavior in later conditions.

The objective of the   research is to test the effect of (i) Salt, (ii) Sugar and (iii) protein independently on the blood pressure level . But, because of the carry over effect, the result of the study cannot meet the objective of the experiment. The reason is: In Treatment 2, the participant is not tested with Sugar alone as decided by the experiment but Salt and Sugar due to carry over effect. Similarly, in Treatment 3, the participant is not tested with Protein alone as decided by the experiment but with Salt, Sugar and Protein due to carry over effect.