Participants enter a research study with unique characteristics that produce different scores from one person to another. For an independent-measures study, these individual differences can cause problems. How can these problems be eliminated or reduced with a repeated-measures study? Check all that apply. In a repeated-measures study, individual differences do not add to the variance of the scores because the same participants are used in all treatment conditions. In a repeated-measures study, you eliminate extraneous changes to the individuals in the sample over time. In a repeated-measures study, both samples consist of the same individuals, eliminating systematic differences between the two samples, which bias the results. In a repeated-measures study, you eliminate the need for the population distribution of difference scores to be normal.