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c.
Chapter 3:
Descriptive Statistics:
Numerical Measures
Objectives:
1.
Calculate and describe the characteristics of
the measures of center.
2. Calculate and describe the characteristics of
the measures of dispersion.
3.
Describe data in terms of center, dispersion,
and skewness.
4. Convert data to standardized values.
5.
Describe data occurrences using Empirical
Rule.
6. Be able to identify outlier.
A.
Introduction – We have looked at
graphical representations and basic
numeric descriptors (i.e.: minimum,
maximum, range, mode) for numeric
data.
In this chapter, we will elaborate
on more sophisticated ways of
summarizing data using numeric
indices.
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View Full Document These numeric indices describe
three
major properties of numeric data
:
1.
Location (Center)
2.
Dispersion (Variation or Spread)
3.
Shape
B.
Measures of Location (Section 3.1)
1.
Mean
– average; value around
which observations tend to
cluster; balance point of
histogram.
a.
Population mean (
μ
)
μ
=
N
X
N
i
i
∑
=
1
b.
Sample mean (
X
)
X
=
n
X
n
i
i
∑
=
1
Example: Audit Data
c.
The mean is susceptible to
(influenced by) outliers.
2.
Median
– the point at which half
the data lie above and half the lie
below
a. If the sample size is odd, the
median is the middle value.
b. If the sample size is even, the
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This note was uploaded on 11/03/2009 for the course ISDS 2000 taught by Professor Nunnery during the Summer '08 term at LSU.
 Summer '08
 Nunnery

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