Hello everyone,
I have extracted data from longitudinal studies that have collected data on pre and post time points. All studies have same time period.
So I have got
N_pre
Mean_Pre
SD_Pre
N_post
Mean_Post
SD_Post
In order to compute the standardised or unstandardised Mean differences, I need to use the denominator SD. What I know is I need the SD of mean difference. Unfortunately this is not mentioned available for many studies. Also it may be computed based on (r=correlation coefficient if it is provided, or other statistics like t etc.)
But I have seen some papers that ignore the above rule and just use SD_Pre or SD_Pooled: (SD_Pre and SD_Post). I am so confused, are we allowed to do that?
Can anyone please guide.
Thank you.
Kind regards
Aziz
I have extracted data from longitudinal studies that have collected data on pre and post time points. All studies have same time period.
So I have got
N_pre
Mean_Pre
SD_Pre
N_post
Mean_Post
SD_Post
In order to compute the standardised or unstandardised Mean differences, I need to use the denominator SD. What I know is I need the SD of mean difference. Unfortunately this is not mentioned available for many studies. Also it may be computed based on (r=correlation coefficient if it is provided, or other statistics like t etc.)
But I have seen some papers that ignore the above rule and just use SD_Pre or SD_Pooled: (SD_Pre and SD_Post). I am so confused, are we allowed to do that?
Can anyone please guide.
Thank you.
Kind regards
Aziz