Discovering Statistics

How do I compare population variances using the f distribution?

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    Graham P


    I am looking to see whether 2 groups differ only in the amount of variance (not the actual scores).

    For example, I am hypothesising that group B has a significantly larger variance than group A (all participants takes part in both condition). I have made up some data below:

    A = 6, 7, 6, 5, 7, 7, 7, 8, 4, 6 (Mean = 6.3, SD = 1.2)

    B = 9, 4, 4, 9, 3, 10, 10, 7, 6, 3 (Mean = 6.5, SD = 2.9)

    So group B has a greater amount of variance than group A, but how do I determine if this is statistically significant (p<0.05). – I am not looking at whether group A scores more than group B (otherwise, I know that I could just do a paired t-test) – only if group B has greater variability.

    I hope that makes sense, but if not I’ll try and explain things a bit better. Please, please, any help would be appreciated. I have been stuck on this for a while.



    Stephen Gorard

    Group B clearly has larger variation. I hope your actual data is larger scale. But the pattern is clear. What more do you want? What do you mean is it ‘statistically significant’?

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