Which of the following is a weakness of independent measures design?

The correct answer highlights a notable drawback of using an independent measures design in research. In this type of design, different participants are assigned to different conditions of the experiment, meaning that each participant only experiences one condition. This can lead to issues related to individual differences—characteristics such as age, gender, personality, and previous experiences can vary widely between groups. If these differences are not evenly distributed, they could influence the results and create variability that is not due to the experimental manipulation itself.

For example, if one group happens to have predominantly more experienced participants while another group has mostly novices, any difference observed could be attributed to those individual characteristics rather than the effect of the independent variable. As a result, without controlling for these individual differences, it’s harder to draw valid conclusions about the effect being studied.

Regarding other options, while ecological validity refers to the extent to which findings can be generalized to real-life settings, independent measures designs are not inherently less ecologically valid compared to other designs. Also, this design does not necessitate a single testing session; multiple sessions could be used across different groups. Demand characteristics can arise in any study but are not uniquely enhanced by independent measures designs; they relate more to how participants might guess the purpose of the study and