bpo-36546: Add more tests and expand docs (#13406)
diff --git a/Doc/library/statistics.rst b/Doc/library/statistics.rst
index fb7df4e..bc841fd 100644
--- a/Doc/library/statistics.rst
+++ b/Doc/library/statistics.rst
@@ -511,22 +511,33 @@
is not least 1.
The *dist* can be any iterable containing sample data or it can be an
- instance of a class that defines an :meth:`~inv_cdf` method.
+ instance of a class that defines an :meth:`~inv_cdf` method. For meaningful
+ results, the number of data points in *dist* should be larger than *n*.
Raises :exc:`StatisticsError` if there are not at least two data points.
For sample data, the cut points are linearly interpolated from the
two nearest data points. For example, if a cut point falls one-third
of the distance between two sample values, ``100`` and ``112``, the
- cut-point will evaluate to ``104``. Other selection methods may be
- offered in the future (for example choose ``100`` as the nearest
- value or compute ``106`` as the midpoint). This might matter if
- there are too few samples for a given number of cut points.
+ cut-point will evaluate to ``104``.
- If *method* is set to *inclusive*, *dist* is treated as population data.
- The minimum value is treated as the 0th percentile and the maximum
- value is treated as the 100th percentile. If *dist* is an instance of
- a class that defines an :meth:`~inv_cdf` method, setting *method*
- has no effect.
+ The *method* for computing quantiles can be varied depending on
+ whether the data in *dist* includes or excludes the lowest and
+ highest possible values from the population.
+
+ The default *method* is "exclusive" and is used for data sampled from
+ a population that can have more extreme values than found in the
+ samples. The portion of the population falling below the *i-th* of
+ *m* data points is computed as ``i / (m + 1)``.
+
+ Setting the *method* to "inclusive" is used for describing population
+ data or for samples that include the extreme points. The minimum
+ value in *dist* is treated as the 0th percentile and the maximum
+ value is treated as the 100th percentile. The portion of the
+ population falling below the *i-th* of *m* data points is computed as
+ ``(i - 1) / (m - 1)``.
+
+ If *dist* is an instance of a class that defines an
+ :meth:`~inv_cdf` method, setting *method* has no effect.
.. doctest::