Sample size for research

#1
Hi there,

I wonder if anyone could shed some light on how to perform a power calculation:

There is not much information available but basically I am looking to analyse the presence of DNA mutation in 200 patients with heart failure with reduced ejection fraction and 200 with heart failure with preserved ejection fraction. What we know:
1. in patients with ischaemic heart failure 18.5% off 200 patients showed the mutation.
2. The mutation is more common as we get older with 10-20% of people over 70 demonstrating the mutation
3. heart failure with preserved ejection fraction more common in patients over 70

Thanks in advance

leanne
 

Karabiner

TS Contributor
#2
So, what is your exact research question? Which statistical analyses do you plan to carry out?
And why do you need a power calculation, although the sample size is already clear (n=400)?

With kind regards

Karabiner
 
#3
We have to justify our choice of the 400 sample size for ethics
The prevalence of this specific DNA is higher in patients with heart failure with preserved ejection fraction than reduced ejection fraction