Justification:

Since, participants produce different scores from one person to another and the independent-measures study is used. The first problem is the large differences in scores of participants because of grouping. Since, groups are independent so, there are chances that 2 groups are formed in such a way that they differ a lot in some characteristics. So, there can be large differences in participants score by grouping only.

Second problem can be the large variance, since, there exist individual differences of score due to which overall variance increases.

Both the problems can be eliminated by using repeated-measures study design because in this study participants in both the groups are same, therefore there will not be grouping error. Also, in repeated-measures study design, individual variance vanishes.

Conclusion:

The problems in independent measures design are grouping error and larger variance because of individual variances. The problems can be eliminated by using repeated-measures design.

Since, participants produce different scores from one person to another and the independent-measures study is used. The first problem is the large differences in scores of participants because of grouping. Since, groups are independent so, there are chances that 2 groups are formed in such a way that they differ a lot in some characteristics. So, there can be large differences in participants score by grouping only.

Second problem can be the large variance, since, there exist individual differences of score due to which overall variance increases.

Both the problems can be eliminated by using repeated-measures study design because in this study participants in both the groups are same, therefore there will not be grouping error. Also, in repeated-measures study design, individual variance vanishes.

Conclusion:

The problems in independent measures design are grouping error and larger variance because of individual variances. The problems can be eliminated by using repeated-measures design.