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Question: understanding the meaning boxplot
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gravatar for farahqureshi5
5 weeks ago by
farahqureshi50 wrote:

Greetings!!

can anyone tell me how to understand the contents of boxplot. what does it indicate

ADD COMMENTlink modified 5 weeks ago by Peter Langfelder1.2k • written 5 weeks ago by farahqureshi50

Bioconductor isn't the right place to ask questions about elementary statistical methods. However Google is your friend and it will surely tell you all you need to know.

ADD REPLYlink modified 5 weeks ago • written 5 weeks ago by Gordon Smyth30k
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gravatar for Peter Langfelder
5 weeks ago by
United States
Peter Langfelder1.2k wrote:

From help(boxplot.stats):

 

    The two ‘hinges’ are versions of the first and third quartile,
     i.e., close to ‘quantile(x, c(1,3)/4)’.  The hinges equal the
     quartiles for odd n (where ‘n <- length(x)’) and differ for even
     n.  Whereas the quartiles only equal observations for ‘n %% 4 ==
     1’ (n = 1 mod 4), the hinges do so _additionally_ for ‘n %% 4 ==
     2’ (n = 2 mod 4), and are in the middle of two observations
     otherwise.

     The notches (if requested) extend to ‘+/-1.58 IQR/sqrt(n)’.  This
     seems to be based on the same calculations as the formula with
     1.57 in Chambers _et al_ (1983, p. 62), given in McGill _et al_
     (1978, p. 16).  They are based on asymptotic normality of the
     median and roughly equal sample sizes for the two medians being
     compared, and are said to be rather insensitive to the underlying
     distributions of the samples.  The idea appears to be to give
     roughly a 95% confidence interval for the difference in two
     medians.

 

ADD COMMENTlink written 5 weeks ago by Peter Langfelder1.2k
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