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Chapter 2
Descriptive Statistics
2.1 Summary of Formulas
1
Commonly Used Symbols
•
The symbol
Σ
means to add or to ﬁnd the sum.
•
n
= the number of data values in a sample
•
N
= the number of people, things, etc. in the population
•
x
= the sample mean
•
s
= the sample standard deviation
•
μ
= the population mean
•
σ
= the population standard deviation
•
f
= frequency
•
x
= numerical value
Commonly Used Expressions
•
x
*
f
= A value multiplied by its respective frequency
•
∑
x
= The sum of the values
•
∑
x
*
f
= The sum of values multiplied by their respective frequencies
•
(
x

x
)
or
(
x

μ
)
= Deviations from the mean (how far a value is from the mean)
•
(
x

x
)
2
or
(
x

μ
)
2
= Deviations squared
•
f
(
x

x
)
2
or
f
(
x

μ
)
2
= The deviations squared and multiplied by their frequencies
Mean Formulas:
•
x
=
∑
x
n
or
x
=
∑
f
·
x
n
•
μ
=
∑
x
N
or
μ
=
∑
f
·
x
N
Standard Deviation Formulas:
•
s
=
q
Σ
(
x

x
)
2
n

1
or
s
=
q
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This document was uploaded on 10/31/2011 for the course STA 2023 at University of Florida.
 Fall '08
 Ripol
 Statistics

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