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Standard Deviations and Relative Standard Deviations?
Hi, hopefully I can explain this simply:
After constructing two calibration curves I have worked out the concentrations of ten samples which I knew an estimated conc of and four unknowns. So I have in all fourteen concentrations.
I need to calculate +/- two standard deviations for these values and then calculate the Relative Standard Deviation (%RSD)
How on Earth do I go about doing this? Anyone who takes the time to help... all of my hugs for you.
2 Answers
- actechkarizmaLv 49 years agoFavorite Answer
Standard deviation is the square root of the sum of the squares of the deviations of each value from the sample mean.
steps
1. calculate sample mean
2. calcuate the deviation of each value to the mean (+ or -)
3. square them and add them
4. square root the sum..
It tell you the average of the deviations of your sample from the mean value..
Relative standard deviation or (coefficient of variation) tells you how much is this deviation in proportion to your mean
also RSD = SD/Mean u can also express it in percentage
Why is this term very important?
You can state that your sample have an average deviation of 10... say your mean is only 2
other person can say that his standard deviation of the samples is 10 where as hismean is 9
which case is better..? obviously the second one because the standard deviation relative to the mean is less..