Question

Puppies were sorted into three groups, based upon which food they preferred when given a choice: Brand A puppy food, Brand B puppy food, or a diet of cooked ground meat. For two months, each group was restricted to its preferred diet (they were no longer given a choice in diet). Measurements for the height, weight, and length of the puppies was taken each week for two months. The puppies in the group with the diet of cooked ground meat had significantly more growth than the other two groups.

What conclusion can be drawn from this study?

A. There is a causal relationship between diet and puppy growth.

B. No conclusions can be made because there was not a group that received a placebo.

C. It is not possible to make any conclusions because there could be lurking variables that were not considered that caused the difference in growth.

D. There is clear evidence of an association between diet and puppy growth, but it cannot be said there is a causal relationship between diet and puppy growth.

I know the answer is D, my question is why?

Answer 1

Correct option:

D. There is clear evidence of an association between diet and puppy growth, but it cannot be said there is a causal relationship between diet and puppy growth.

Explanation:

The finding of the experiment is:

The puppies in the group with the diet of cooked ground meat had significantly more growth than the other two groups: Brand A puppy food and Brand B puppy food.

From this finding, we conclude:

There is clear evidence of an association between diet and puppy growth,

But, it cannot be said there is a causal relationship between diet and puppy growth because of the following argument:

Correlation does not imply causation. Correlation indicates that the two variables are associated. Causation implies that one variable causes the other variable. Though we note the two variables (1) diet and (2) puppy growth are directly associated, there are many factors which can cause puppy growth other than diet like proper exercise, absence of diseases due to proper care and preventive measures, amicable surroundings which make the puppy happy and healthy and these Confounding variables have not been controlled in this experimentation and hence it cannot be said there is a causal relationship between diet and puppy growth.