Chromatography Forum

I would like to ask how to calculate interday precision

Day 1 3 replicates
Day 2 3 replicates
Day 3 3 replicates.....

if i calculate the mean value and standard deviation for interday CV%......
whether using all 9 replicates (n=9) or using 3 mean value (n=3)???

Please kindly advise me

Thank you

I would use n=9. I feel it's better to use the mean of the actual data points instead of the mean of the three daily means.