Microarray Quartile Analysis

Question

[Ss]

I was reading a paper on Microarray analysis myeloma.

link text

I did not understand the Statistical part under Material and Method section where they talk about quartiles.

Specifically, log-rank tests were performed for quartile 1 (Q1) versus Q2 through Q4 and Q4 versus Q1 through Q3 in order to identify under- and overexpressed prognostic genes, respectively

Can someone please explain this to me? Thanks

Answer 1

[David Quigley]

Wikipedia: quartile.

They're dividing the total distribution of expression values into four equal groups and looking at the highest and lowest groups.

[Chris Evelo]

Well... compared the highest and lowest to all the others. So actually the only thing they did not compare were the two central quartiles with each other. Still +1 for your clear and simple explanation

[David Quigley]

I was perhaps a bit too terse. I was going for somewhere between "google the word quartile" and investing 20 minutes I don't have to spend in writing a definition of quartiles.