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ANOVA with Repeated Measures for non-Normal data?

• 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

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

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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

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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!