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Thread: Checking my approach - Mann whitney

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    Checking my approach - Mann whitney




    Hi everyone

    I was wondering if I had used the correct approach to analyse my data. I have four groups of people answering a survey and taking part in several tests. I am analyzing their test scores looking for differences between the groups. I have used the mann whitney test. Is this OK? Also it is important for me to mention that the sample sizes are different. I have read that this doesnt really matter. I also used a Kruskal wallis test. I was wondering if this was the correct approach?

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    Re: Checking my approach - Mann whitney

    Mann Whitney is for two groups
    Kruskal-Wallis is for two or more groups so you need this one

    Remember the hypotheses and assumption for Kruskal-Wallis are not the same as ANOVA. If you want to compare medians the distribution of scores in each group must have the same shape. Otherwise the test is simply testing differences in shape of the distribution. Groups do not have to be the same size

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    Re: Checking my approach - Mann whitney


    Hi,

    Thanks for the reply. Yes, sorry re reading my question I realise that I wasnt very clear. I used Mann-whitney to test the differences between two groups in particular and then Kruskal-Wallis to look for overall significant differences between all four groups. I used these because I couldnt be certain that my data was normally distributed as I had a small sample size and so didnt use ANOVA. Yes overall I know that they should have the same shape. I think my worry is that one of the group has a very small sample size and so it is difficult to ascertain whether or not it has the same shape as the others.

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