Hello dear colleagues!
I want to present my results regarding water vapour transmission rate. I have 5 samples and I worked in triplicate. Do I apply the formula for each sample (1a, 1b, 1c, 2a, 2b, 2c etc) and then calculate the mean and SD or do I calculate the mean value and SD for each sample (1, 2, 3 etc) and then apply the formula?
the formula used is (initial weight-final weight)/ (areax24)
So should i use (initial weight of sample 1a - final weight of sample 1a) / (areax24) and calculate the mean and SD for sample 1
or calculate mean and DS of samples 1a, 1b, 1c and apply formula as(mean of initial weight of sample 1 - mean of final weight of sample 1) / (areax24)
I want to present my results as the number given by the formula +/- DS
The interesting information usually is the mean (expectation) and the standard deviation between samples. You use the technical replication (3 measurements per sample) only to get a more precise values per sample. Unless you want to show that a particular method of measuring the WVTR is more precise, you should use only the averages of the replicates.
For each sample, you first calculate the average of the three measurements (a,b,c). Then you will have 5 values (averages). Use these 5 values to calculate the standard deviation. (you can calculate the mean from these 5 values, too, but also from the 15 original values - this does not matter).
If you just want to describe what values you measured, I'd suggest to give the range instead (smallest and largest value of the 5 averages). The mean, and particularly the standard deviation, are not very robust and possibly not very useful measures to describe a small sample (of only 5 values). It may even be possible simply to list these 5 values - so the whole and complete information is provided.
Samuel Oluwaseun Adeyemo Thank you very much for your answer! I really helps.
