1
Descriptive Statistics
Objectives:
(Chapter 3, Decoursey)
- To understand the definition of
, median,
variance, standard deviation, mean absolute
deviation and coefficient variation and calculate
these quantities.
- To calculate some of these quantities using the
statistical functions of
.
Descriptive Statistics
Arithmetic Mean:
∑
=
i
x
N
or
x
1
μ
is the mean of a sample.
x
is the mean of a population.
μ
N is the total number of data points.
i
x
is the i
th
data point in the sample or population.
Descriptive Statistics
Median:
If all the items with which we are concerned
are sorted in order of increasing
(size),
from the smallest to the largest, then the median is
the middle item.
If the number of the items is odd, the median is the
middle item.
e.g.
12, 13, 21, 27, 31
The median is
.
If the number of the items are even, the median is given
by the arithmetic mean of the two middle items.
e.g.
12, 13, 21, 27, 33, 37
The median is (21+27)/2=24.
Descriptive Statistics

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