Transcript No Slide Title

Slide 1
Statistics Workshop
Tutorial 2
•
Frequency Distributions
• Histograms
Measured Cotinine Level in
Three Groups
• The data reproduced in the next slide were obtained
as part of the National Health and Nutrition
Examination Survey.
• The data values consist of the measured levels of
serum cotinine (in mg/ml) in people selected as study
subjects. For more information read the chapter 2
opening problem. We’ll use the data to illustrate the
vocabulary of chapter 2.
Slide 3
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Frequency Distributions
Slide 4
 Frequency Distribution
lists data values (either individually or by
groups of intervals), along with their
corresponding frequencies or counts
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Lower Class Limits
Slide 5
are the smallest numbers that can actually belong to
different classes
Lower Class
Limits
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Upper Class Limits
Slide 6
are the largest numbers that can actually belong to
different classes
Upper Class
Limits
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Class Boundaries
number separating classes
- 0.5
99.5
Class
Boundaries
199.
5
299.
5
399.
5
499.
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Slide 7
Class Midpoints
midpoints of the classes
Class
Midpoints
49.5
149.5
249.5
349.5
449.5
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Slide 8
Class Width
Slide 9
is the difference between two consecutive lower class limits
or two consecutive lower class boundaries
100
Class
Width
100
100
100
100
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Relative Frequency Distribution
Slide 10
relative frequency =
class frequency
sum of all frequencies
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Frequency Tables
Copyright © 2004 Pearson Education, Inc.
Slide 11
Histogram
and
Relative Frequency Histogram
Figure 2-1
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Figure 2-2
Slide 12
Shapes of Distributions
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Slide 13
Reasons for Constructing
Frequency Distributions
Slide 14
1. Large data sets can be summarized.
2. Can gain some insight into the nature of
data.
3. Have a basis for constructing graphs.
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Constructing A Frequency Table
Slide 15
1.
Decide on the number of classes (should be between 5 and 20) .
2.
Calculate (round up).
class width

(highest value) – (lowest value)
number of classes
3.
Starting point: Begin by choosing a lower limit of the first class.
4.
Using the lower limit of the first class and class width, proceed to
list the lower class limits.
5.
List the lower class limits in a vertical column and proceed to
enter the upper class limits.
6.
Go through the data set putting a tally in the appropriate class for
each data value.
Copyright © 2004 Pearson Education, Inc.
Slide 16
Now we are ready for
Part 7 of Day 1