# sample pool - (Dec/15/2010 )

Well, then two values, one of the treatment and one of the control. But this are still not means, but two single measurements.

You cannot measure a mean, but only calculate it from several measurements, counts etc.

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.

ok... i agree that is the only way we can get valid data.at least three values are required to calculate SD and significance.

rkay447 on Sat Dec 18 14:22:05 2010 said:

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.

An idea to make it a bit clearer perhaps. You can calculate mean and standard deviation, if you think your approach out:

You pool the samples in the treatment (and control), let's say 8 samples.

You measure, the result is: 89.0 mg protein in pooled sample

Mean = 89.0 mg/8 = 11.125 mg protein per sample.

Standard deviation = 0 (all samples have the same protein content, because of pooling)

It's possible to tell if the two samples are statistically different from each other if the the specs ( as VC at the same level) from the method are known.

We had a simular problem and after consulting our biostatistic department we could tell if the groups where different or not.

As I remember one of the big issues was the presence of very abnormal values in 1 one of the samples and the confidence of the test depended strongly of the number of samples in the pool.

sorry didnot understant..what is specs..VC?

Gerard on Mon Dec 20 10:25:37 2010 said:

It's possible to tell if the two samples are statistically different from each other if the the specs ( as VC at the same level) from the method are known.

We had a simular problem and after consulting our biostatistic department we could tell if the groups where different or not.

As I remember one of the big issues was the presence of very abnormal values in 1 one of the samples and the confidence of the test depended strongly of the number of samples in the pool.

I think that Gerard was talking about the error of the machine you used to measure the assay on. This is still not really valid for statistical analysis as it doesn't prove anything - other than that you measured two samples and they are different... you can make no claims about that biologically, as it could have been that one of your pooled samples was really different from all the others - which is giving a flase impression of the differences.