Question: understanding the meaning boxplot
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farahqureshi50 wrote:

Greetings!!

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

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 24 months ago • written 24 months ago by Gordon Smyth36k
Answer: understanding the meaning boxplot
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Peter Langfelder1.8k 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.