Re: median of two groups are statistically significant

Posted by Bruce Weaver on Aug 24, 2011; 2:22pm
URL: http://spssx-discussion.165.s1.nabble.com/median-of-two-groups-are-statistically-significant-tp4723704p4730619.html

I just noticed that I received this off-list reply at the hotmail address I use for posting here.  (I only check that inbox occasionally, as it says in my sig file below).  I'm posting it here because others might have some ideas about what can be done.

--- start of off-list reply ---
Hi Bruce,

Thanks! The data does not follow a normal distribution in any of the groups. I am dealing with bacterial HPC counts. It ranges from 0 to 10^10 in different groups. So, I want to compare if the median count in different groups statistically significant or not.

Thanks again

Nsaha6
--- end of off-list reply ---

If I follow, you have k groups, and for each group there is one data-point, which is a bacteria count ranging between 0 and 10^10.  Correct?  This is outside my research area.  What is typically done in your field?  

Bruce Weaver wrote

What is the nature of the data?  Is it reasonable to assume that the distribution shape is the same in both (or all) groups?  To see why I ask that question, see the "Do non-parametric tests compare medians?" section in Chapter 10 of "Statistics at Square One".

http://resources.bmj.com/bmj/readers/readers/statistics-at-square-one/chapter-10-rank-score-tests

HTH.

Nabaneeta Saha wrote

Hello All,

What is the right statistical test to determine whether the median of multiple
groups are statistically significant or not?

Thank you for your help,

Nsaha6

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