**Answer:**A single number describing some features of a frequency distribution is called descriptive statistics. There are various ways in which frequency curves can differ from one another. Even though the ‘general’ shapes of the curves are the same (the area under them is already made equal by the strategy of plotting the percent density), the details of the shape may change.Thus, a kind of an ‘average’ location of the distribution along the variable

There are three measures of
central tendency-Mean, Median, and Mode.

Again Mean is of three types:

1.
Arithmetic Mean (A.M),

2.
Geometric Mean (G.M), and

3.
Harmonic Mean (H.M).

The words ‘mean’ and
‘average’ only refers to Arithmetic Mean.

**Mean**

The mean is also known as
the average. Most of us look at an average as a way of smoothing over the
variations in data and obtaining a single representative number.

**Arithmetic Mean**

Arithmetic Mean is the most
widely used measure of central Tendency. Arithmetic mean is defined as the
ratio between the sum of the observations and the number of observations.
Arithmetic mean can be computed in two ways: i) Simple arithmetic mean, and ii)
Weighted arithmetic mean. In case of simple arithmetic mean, equal importance
is given to all the observations while in weighted arithmetic mean, the
importance given to various observations are different.

**Geometric mean**

Let the number of
observations are n. The geometric mean is a measure of central tendency which
is equal to the nth root of the product of the observations. The formula for
the geometric mean (GM) is:

GM=(X

_{1}X_{2}X_{3}……X_{i}…..X_{n})^{1/n}, where X_{i }is the ith observation.
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