Unfair comparison

Dissimilar measurement

Look out for comparisons of nutrition interventions where what happened was measured differently in the comparison groups.

Sometimes, in a study, outcomes were measured or detected differently in intervention comparison groups. When this is the case, it is hard to know how much the different measuring methods affected the study results.

For example, the people measuring the outcomes in a comparison of interventions for depression might believe that omega-3 fatty acid supplements are better than placebo. If they know who received the omega-3 fatty acid intervention, they may be more likely to think that those people were less depressed.

One way of keeping this from happening is not to let the people measuring the outcomes (“outcome assessors”) know which people got which intervention (to “blind” them).

REMEMBER: Think about whether outcomes were measured the same way in the different intervention comparison groups of a study.