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Non-Equivalent Control Groups Design/ Quasi-Experimental Design

Posted: Thu Jul 14, 2016 6:37 am
by ella_n

I would like to know what analysis I should choose to compare the difference between 3 groups. Here's the design:

I have 3 conditions (pictures of either underweight, normal weight, or overweight models, as C1, C2, C3), and I assign the participants to each condition according to their own BMI (G1, G2, G3), so that I will make sure there are at least 9 participants in each combination (e.g. C1G1, C1G2, C1G3, C2G1..., a total of 9 combinations). What statistical test should I use if I want to compare the difference between groups in terms of, say body image and weight-loss desire? What method should I choose if I want to control the between-group difference before starting any analysis?

Since the sample size of each group is around 9, is it also a concern for small sample size for running statistics? How can I know how many participants is enough?

Sorry I have a lot of questions in my mind, but I would be really grateful for your answer.