
when we pool samples how do we calculate standard deviation and variance?
thank you
Posted 15 December 2010 - 05:39 PM
Posted 16 December 2010 - 03:23 AM
Posted 16 December 2010 - 07:49 AM
"pool samples"...do you mean combine sample volumes into one container? Or obtain samples and have them as a single population?
Posted 16 December 2010 - 01:02 PM
Posted 16 December 2010 - 03:25 PM
Never came across this approach. Usually collect samples from control and experimental groups and compare them (compare the group as a whole or break down into subsets).
If pooling samples from experimental then you would need to do same with control.
Individual samples should be taken from two groups then analytically compared.
Posted 16 December 2010 - 08:02 PM
Posted 17 December 2010 - 01:40 AM
Posted 17 December 2010 - 02:14 AM
A single lie is reproachable; a million lies is a statistic.
D. J. T.
Posted 17 December 2010 - 04:47 PM
For most experiments not the volume but the concentration of amount of substance matters.
I don't know whether your experiments are exceptions, but if not, then why don't you just fill up your 10 µl sample to 50 µl?
Posted 17 December 2010 - 04:50 PM
I agree with bob1, you neither have a mean nor standard deviation: if you pool your samples to one sample and then measure, you have just one data point.
Chakchel's idea would be a solution (if it's possible), then you have several measurements and can calculate mean + SD.
Posted 18 December 2010 - 05:11 AM
A single lie is reproachable; a million lies is a statistic.
D. J. T.
Posted 18 December 2010 - 06:22 AM
Posted 18 December 2010 - 06:03 PM
I agree. You can not consider the value you obtain from your pooled samples a mean since you don't know the value of each individual sample that made up the pooled. You are going to have to do the experiment three times and make three independent pooled samples to obtain the needed values for statistics.
Posted 19 December 2010 - 06:20 AM
A single lie is reproachable; a million lies is a statistic.
D. J. T.
Posted 20 December 2010 - 02:25 AM
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