Section 2.1 – Organizing Qualitative Data
Frequency Distribution (frequency table)
– A list of data values (grouped into classes/categories)
along with their corresponding frequencies.
Example
:
A phlebotomist draws the blood of a random sample of 50 patients and determines their
blood types as shown below.
Create a frequency distribution for the blood types.
O
O
A
A
O
B
O
B
A
O
AB
B
A
B
AB
O
O
A
A
O
AB
O
A
B
A
O
A
A
O
A
O
A
O
AB
A
O
B
A
A
O
O
O
O
A
O
O
A
O
A
O
Relative Frequency
=
the proportion (or percent) of observations within a category.
Relative Frequency =
s
frequencie
all
of
sum
frequency
class
Example
:
Create a relative frequency distribution for the last example
Blood Type
Frequency
Blood Type
Relative Frequency
1
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Bar Graph
–
Constructed by labeling each category of data on the
x
axis and the frequency (or
relative frequency) on the
y
axis.
Rectangles of equal width are drawn for each category and the
height of the rectangle represents the frequency.
Bars do not touch.
Example
:
Draw a frequency bar graph for the last example.
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 Spring '12
 LisaJuliano
 Frequency, Frequency distribution, Bar chart, Histogram, Eye color, relative frequency

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