Question

Cocoa and blood flow- A study of blood flow involved$27$healthy people aged$18$to$72$.

Each subject consumed a cocoa beverage containing$900$milligrams of flavanols daily for

$5$days. Using a finger cuff, blood flow was measured on the first and fifth days of the

study. After$5$days, researchers measured what they called “significant improvement” in

Blood flow and the function of the cells that line the blood vessels. What a flaw in the

design of this experiment makes it impossible to say if the cocoa really caused the

improved blood flow? Explain your answer.

Short answer

No flaw in the design of the experiment can make it impossible to say if cocoa cause improvement because no control groups are formed in order for the comparison purposes.

Step-by-step solution

Given information 

We are given a study of the blood flow of healthy people of different age groups, and we have to find the flaw in the design of the experiment that makes it impossible to say if the cocoa really caused the improved blood flow.

Explanation

In the given case study, there is no purpose for comparison due to the absence of control groups. It is not given any effects that could affect the blood flow in the human body by cocoa. There is no information if it is a placebo effect, and not even aware of the effect of flavanol on the human body. Hence, there is no flaw in the design of the experiment.