If your triplicate is one sample , and other triplicate is 2nd sample and ........

then average and standard deviation take for each triplicated group as single sample. like that for others.

then you take again average of all sample group and deviation as one group now you have only one graph .. if you are asking like that , if you want different elaborate the question.

Intra-assay errors are usually smaller than inter-assay errors. I would average the mean obtained from each of the 8 triplicates and use those means to plot the global mean +/- SD. Separately, I would try to obtain a measure of the intra-assay error by averaging, for example, the coefficient of variation of each of the 8 triplicates (CV = SD/mean x 100): i.e. CV triplicate 1 = SD1/MEAN1 x 100; CV triplicate 2 = SD2/MEAN2 x 100 ... etc. Average CV = sum CV triplicates / 8. I would hope for CVs less than 5-10%.

How to Calculate the Standard Deviation:  ​

Please have a look in to the attached link to do it using Excel

https://www.biologyforlife.com/standard-deviation.html

You may want to use programs lie Excel or SPSS for easier and more convenient calculation.

You may want to use programs like Excel or SPSS for easier and more convenient calculation.

you can try the statistical packages like minitab, stats, SPSS or even more easier excel

https://www1.udel.edu/htr/Statistics/Notes/class12.html