Calculating Effect Size (Cohen's d) for a Paired-Samples T Test 

Awesome, excellent video! I clicked myself through dozens websites, nowhere I understood how the d is computed. Here you explained it very easy, thank you!

Second time to watch and more stood out on the significance of Cohen's d and how it relates to the p value. Thanks Dr. Grande, very helpful.

Thanks for the guidance. It was easy to understand.

very good explanation, thank you, I was able to understand everything , and great that you have used these two different method! :) Have a good one! :)

Thank you so much. This was crystal clear, and extremely helpful for my first unit of stats in my psychology grad dip.

Thank you for the explanations Dr. Grande, always very useful. This is the second time I see someone referring to =0.8 as large and citing Cohen. But I read the book and its says d=0.2 small, d=0.5 medium, d=0.8 large (p. 25 to 27). I couldn't find any reference of him talking about intervals. Most importantly, in Illustrative Example 2.6 (p. 50) he gets d=0.4 and he himself classifies it as "small to medium value". I've seen other researchers saying 0.7 large, and citing Cohen. And others simply saying that it is "around" 0.2, 0.5 and 0.8, which is what I found in the book. I'm using the "around" version so far, but I'm worried to be wrong. Please, could you tell me on what page of Cohen (1998) is the reference where he says that 0.2, 0.5 and 0.8 are the lower bounds and not anchors around which small, medium and large can be considered?

Thank you for running this. I particularly appreciated how you showed gathering the information from the SPSS output for the equations in Excel

When I want to calculate Cohen's d for two treatments from the same sample and I run a paired t-test in Excel, it doesn't give me the SD, so I don't know how to calculate Cohen's d by the SD by the mean. Any chance you can help?

Dividing the mean difference by the standard deviation of the differences does not conform with the definition of Cohen's d. With this computation, if each person in the sample would increase or decrease with the exact same amount (however small or large), then this would yield an effect size of (minus) infinity. The proposed 'effect size' says more about the variability than about the strength of the effect. To obtain an actual effect size, one should divide the mean difference by the pooled pre- or post-test standard deviation.

Hi, if i got negative value for my effect size, what does it indicate? My test is significant to test for the increase of gratitude level

Thanks for the explanation! May I ask how to apply the effect size to the results of Wilcoxon test? (or what criteria should be considered when it comes to this non-parametric test) Is the computation equal? (d= mean difference/Std. deviation of the difference) Thank you

It was very useful. Thank you very much . ✅ 😊👍

Thank you very much! very clear and very helpful. Best regards,

Hi, thanks for the explanation. I was wondering if you would be able to explain how researchers present the effect size in academic papers?

Thanks for the great video - how would I compute the 95% confidence interval around this effect size estimate?

What about if i use the formula used by Dunlop et al. (1996)? d = t calculated times the square root of (2*(1-r))/n?

We need the excel sheet. how can we get it?

Really helped! Thanks very much!

Could you explain why the effect size is different using the calculation mentioned in Your video than the more commonly used method for calculating Cohen's d: d=(M1-M2)/SD pooled

thank you so much! This video is extremely helpful!!!!! C:

Otro excelente video! Gracias Dr. Grande!

Excellent explanation of Cohen's d calculation using paired samples

Again excel required many functions to reach a result. Hands on will provide a better understanding. Good start

i had a problem calculating cohen's d. my t value is 7.00 and my N=20 and my calculation turned out to be more than 1... how is that possible?

Thanks man this video helped me with my dissertation

Thank you so much! Is it necessary to calculate cohen's d if we reject hypothesis null? what if i get negative value for the value of cohen's d?

Super helpful Dr. Grande. Thank you for this!

Thank you very much for the clear video. Can you give a reference for this calculation?

This was so helpful, thank you very much!

if you fail to reject the null hypothesis in a paired samples t-test, does that mean you don't have to calculate the effect size? Therefore, you only calculate the effect size when you reject the null hypothesis?

Is it possible to get your excel ?

Dr. Grande, Thank you! I am post-PhD and found your video very helpful!

Thank You, very useful

Thank you su much! I learned more from you than my statistics teacher.

The best I have came across, please do more videos , Thanks

Fantastic video, thank you!

This video was of great assistance!! Thank you so much!!

Thank you very much for your excellent videos

kind of looks like a dz to me? but I'm not expert

Do you have a reference for second equation? I need to write my paper..

Hello , I found it more than 2 , what is the problem please.

You are great!

but how about if we have more than one pair?