Unfair comparison

Dissimilar comparison groups

Look out for comparisons of nutrition interventions where the comparison groups were not alike.

For a comparison of interventions to be fair, the people in the comparison groups should have been as similar as possible at the start of a study. If groups were not similar, this may have affected the results, thus being an unfair comparison. We cannot know if what happened in the study was due to the groups being dissimilar, the nutrition interventions that were compared, or both.

For example, in a comparison of a nutrition supplement versus a placebo, if the group that gets the nutrition supplement is healthier at the beginning of the study than the group who gets the placebo, the nutrition supplement could look like it works better than it actually does.

The best way to make sure that the people in both groups are alike is to use a chance process to decide who gets which nutrition intervention. Random allocation, like flipping a coin or using a computer to generate a list of random numbers, is the preferred chance process.

REMEMBER: Think about whether who got which nutrition intervention was decided by chance (randomly) in a comparison of interventions, and if the people in the comparison groups were similar at the start of the study.