How to compute sample size for comparing heart rate and blood pressure responses between two different groups of people?
you can find the research paper on comparing heart rate and blood pressure responses. or you
you can do pilot study
find the variability bet them..
I was using G Power analysis, this application should be free online, you set some parameters and it tells you sample size you need. Hope that helps a bit
Good luck
Dr Shinha
Maybe am reading beyond your query too much,.. so some of my reply may be off target. Nonetheless, if you are comparing two distinct groups sans intervention, then the above will suffice.-- but if comparing two groups drawn from same population with one an intervention and other a control (or alternate intervention), then there are experimental options with differing power. In this latter situation, you may measure HR and BP in both groups before the intervention and then use as control for individual differences vs. not control for the differences.
ALVAH
PS HR variability (HRV) --- which may be analytically divided into two components reflecting mental and physiological stress -- which often hold utility for researchers concerned with BP and HR...and may be captured with HR.
Sample size calculations depend on the effect size that you are trying to detect. For comparing two groups of people using means, the effect size is the difference between the means. Smaller differences will require larger sample sizes to detect.
You need to specify what is the minimum difference between groups that is of real-life significance, and base your sample size calculation on this difference. You can then calculate the numbers using any software. GPower, already mentioned, is excellent, and free.
I agree with Ronán, but also you can compute very easily the sample size you need, just using the following formula:
me= 2x ( SD/ N0.5)
Where me= margin error
SD= Standard deviation of distribution values
N= Sample size
So you can perform a samll pilot study and then use mean and SD to compute the optimal N you need to get the desired margin error
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