If an outcome is measured differently in two comparison groups, differences in that outcome may be due to how the outcome was measured, rather than because of the intervention received by learners in each group.
For example, if outcomes are assessed through open-ended questions in one group but multiple choice questions in another, the difference in groups may be due to how they were assessed, rather than due to the effect of an intervention.
BEWARE of relying on the results of intervention comparisons if outcomes were not measured in the same way in the different comparison groups. The results of such comparisons can be misleading.
REMEMBER to check if outcomes were assessed similarly across groups.