compute effect size

[Aurélie_D]

hello,

I want to compute the effect size of a variable.

mean group1 = 10,978

mean group 2 = 9,228

standard deviation 1 = 0,8402

standard deviation 2 = 0,5767

correlation = 0,59105

I calculated the effecct size with g*power, but the result is 2,56. This is a very high value ?

Can I compute this in SAS with this given information, or am I doing something wrong?

greetings,

Aurélie

[Reeza]

Do you have access to the raw data? What do you mean by EFFECT size? I'm used to see it in context of regression models not just summary statistics. 

[Reeza]

Assuming this paper is talking about the same thing you are, see the macro included. 

http://analytics.ncsu.edu/sesug/2012/SD-06.pdf

[Aurélie_D]

hello,

thank you for the reaction. I have a dataset with 1 group measured 2 times, so I used a paired t-test. But as you see when I calculate this in g*power I get a huge effect size. The effect size that I get when using method 1 is different than when I use method 2.

METHOD 1

I compute first the effect size in g*power in the additional window (effect size = 2,56).

Then I use this value to calculate the power (power = 1).

METHOD 2

I first calculate the power in SAS (power = 0,9999).

Then I use this power value to calculate the effect size in G*power (effect size = 0,68)

Can somebody explain this?

greetings,

Aurélie