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Calculate pooled standard deviation f... |
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Rulph S posted on Monday, December 28, 2015 - 4:03 pm
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Hello, I wanted to ask how I can calculate the pooled standard deviation from a TECH4 output? I understand I get the standard deviations by using the square root on each of the measures on the diagonal from the covariance matrix - but how does this lead me to the pooled standard deviation? Specifically, I want to calculate Cohen's d, and substracting the mean of T2 from the mean of T1 is not hard, but what is a simple formula to obtain the pooled standard deviation for the division? For example, I have the following numbers: Mean of T1: 0.000 Mean of T2: -0.063 And on the diagonal: Variance (T1): 0.679 Variance (T2): 0.649 Variance (I): 0.679 Variance (S): 0.414 This leads to... d=(-0.063-0.000)/???? I would be glad if you could help me with this! |
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Because you seem to have the T1 mean fixed at zero only the mean of T2 has variability so no need for pooling. I assume that this concerns time 1 to time 2 change. Just divide by -0.063 by the square root of the T1 variance which tells you how big of a change has taken place in the T1 metric. |
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Rulph S posted on Monday, December 28, 2015 - 4:45 pm
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Oh that's great - thanks a lot! So it's just (meanT2-meanT1)/sdT1 I'll use that, thanks again. |
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