1 2 Previous Next 17 Replies Latest reply on Nov 14, 2018 11:30 AM by Shinichiro Murakami Go to original post
• ###### 15. Re: Formula for R2 and P values for Trend Lines

Hi Bora Beran ,

Thanks for sharing the twbx for the LOD calculations.  I was looking at the t-critical calculations. The calculations uses SUM(1) -2 .   I would really appreciate if you can explain why we are doing df -2 for the calculations.

If anyone else knows the answer please feel free to jump in.@

• ###### 16. Re: Formula for R2 and P values for Trend Lines

Bora no longer works at Tableau so he likely won't reply.

• ###### 17. Re: Formula for R2 and P values for Trend Lines

HI Nellie,

This might be too simple but hope help a bit.

How should I understand the (n-2) degrees of freedom in correlation analysis? - Quora

or

1. 1. Degrees of Freedom.

The term degrees of freedom refers to the number of scores within a data set that are free to vary.  In any sample with a fixed mean, the sum of the deviation scores is equal to zero. If your sample has an n  equal to 10. The first 9 scores are free to vary but the 10th score must be a specific value that makes the entire distribution equal to zero. Therefore in a single sample the degrees of freedom would be equal to n - 1. The degrees of freedom for a correlation is slightly different because n equals number of pairs not simply sample size. Therefore, the degrees of freedom for a correlation in n - 2. So to calculate the degrees of freedom you simply take the number of pairs and subtract two. For our data set of depression and self-esteem scores the degrees of freedom are calculated the following way:

Thanks,

Shin

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