###### Asked in Math and Arithmetic, Statistics, Algebra

# What is a descriptive statistic?

## Answer

###### Wiki User

###### 12/07/2009

A descriptive statistic is a numerical summary of a dataset
(e.g. a sample). There are four types of descriptive statistics
that are commonly used: * **Measures of central
tendency****:** the central or most common value. #
**mean** - There are several different types of mean, but by far
the most commonly used is the *arithmetic* mean, which is
simply the sum of the measurements divided by the number of
measurements. This is typically what people refer to as the
average. # **median** - value for which exactly half the
measurements lie above and half below # **mode** - most
frequently occurring measurement in a category

* **Measures of variability:** the normal spread of values
around the central value. # **standard deviation** - the mean of
the squared deviations from the mean. 1 standard deviation is the
range around the mean in which roughly 62% of the values of data
will fall. # **quartiles, deciles, centiles** - divide the
values in the data set into equal quarters (or tenths, or
hundredths) by number of data points, to show how the values of the
data points cluster around the center. # **correlation** - (for
two variables) how closely the distribution of values in the two
variables are related.

* **Measures of shape:** what the data looks like. #
**skew** - whether the data is balanced around the mean, or
whether weighted towards one side or the other # **kurtosis** -
the 'peaked-ness' or 'flatness' of a distribution.

* **Measures of size:** # **sample size** - how many
points have been analyzed