How many participants would be needed for a two-factor experiment with both factors being within subjects, and with two levels of factor a, three levels of factor b, and with n = 5 scores in each treatment condition?

5

Explanation:

When calculating participants in a factorial design research study always look at the number of conditions or treatment conditions. The reason is that for each condition, the two variables or factors will be analysed at different levels. Here, factor A has two levels and factor B has three levels. Therefore, for each condition at least one participant will be tested against the two levels of factor A and three levels of factor B. Since, 5 treatment conditions are considered hence, 5 participants are required.

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