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  • 1.  ANOVA with Repeated Measures for non-Normal data?

    Posted Mon November 08, 2021 10:01 AM
    Hello,

    I would like to get some advice to analyse some data. Here are the key features.
    1. The data is not Normally distributed.
    2. It is not independent, that is, I am comparing the same group of people over three time periods.
    3. The data is numerical, from 0 to 100.
    4. The data consists of three groups, same individuals, samples at three different time frames.
    5. there is  quite a bit of missing data, specially in the 1 and 2 month periods.

    I need to compare the means of those three groups.

    Here is a mock example of the data. Actual data is just a bit bigger, with 40 individuals, not 10.

    Name  Baseline  1_month 2_months
    P001 81.22 100 N/A
    P002 56.23 75 68.68
    P003 40 40 N/A
    P004 100 N/A 100
    P005 40 N/A N/A
    P006 73.33 40 N/A
    P007 0 39.36 18.69
    P008 94.44 90.55 85.55
    P009 15.56 N/A N/A
    P010 83.26 N/A N/A

    Any advice would be welcome!

    My first conclusion was to do a ANOVA with Repeated Measures, until I realised the data is not Normally distributed... I tried transfroming it but that didnt make it Normal either. Although I only tried to do it with Log10.

    Thank you for any help!

    Freddy

    ------------------------------
    KARL GRUBER
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  • 2.  RE: ANOVA with Repeated Measures for non-Normal data?

    Posted Mon November 08, 2021 10:11 AM
    Hi.

    1). Have you considered non-parametric analysis?

    2). For parametric analysis, if I remember correctly, the important thing is not the distribution of the test variables per se, but the distribution of their sample means.






  • 3.  RE: ANOVA with Repeated Measures for non-Normal data?

    Posted Mon November 08, 2021 10:18 AM
    Thanks

    No, I have not considered non-parametric analyses. do you have one in mind? I think the issue is the non-independence of my data.






  • 4.  RE: ANOVA with Repeated Measures for non-Normal data?

    Posted Mon November 08, 2021 10:31 AM
    No. Perhaps this helps?

    https://statistics.laerd.com/spss-tutorials/friedman-test-using-spss-statistics.php

    ------------------------------
    Rick Marcantonio
    Quality Assurance
    IBM
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  • 5.  RE: ANOVA with Repeated Measures for non-Normal data?

    Posted Mon November 08, 2021 11:26 AM
    Thanks!