# Median of Medians calculation

I do a bunch of Real Estate Reporting and the Median price is often reported. Particularly by the NAR (National Association Of Realtors) ,,, How can this be,, As best I can figure they only get the Medians from each area,, so how should they calculate a national median, a median of medians a a simple average of medians or weighted average of medians or....??? How valid can it be,, I know that the NAR is not getting the total transaction table so can a reasonable representation of Median (nationally be done? Particularly since regional density and prices and market variances are so large now?

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Can you please work on the style and clarity of your question? –  mbq Nov 11 '10 at 23:13
if I understand this correctly, dartdog wants to know whether the median of medians is the can be used to calculate the median of the whole sample, i.e. if $M=M_1 \cup M_2 \cup \ldots \cup M_k$ then median($M$)=median(median$(M_1)$,median$(M_2)$,$\ldots$,median$(M_k)$)... –  psj Nov 13 '10 at 19:23