Download Finding Normal Percentiles by Hand

Chapter 6
The Standard Deviation
as a Ruler and the
Normal Model
Copyright © 2010 Pearson Education, Inc.
CLASSWORK
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Textbook page 132 #’s 15, 16, 17, 18
Copyright © 2010 Pearson Education, Inc.
Slide 6 - 2
The First Three Rules for Working with
Normal Models

Make a picture.

Make a picture.
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Make a picture.
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AND…when we have data
 make a histogram to check the Nearly Normal
Condition to make sure we can use the Normal
model to model the distribution
Copyright © 2010 Pearson Education, Inc.
Slide 6 - 3
Finding Normal Percentiles by Hand
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When a data value doesn’t fall exactly 1, 2, or 3
standard deviations from the mean
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
we can look up the percentile in a table of
Normal percentiles.
Table Z in Appendix D provides us with normal
percentiles
 many calculators and statistics computer
packages provide these as well
Copyright © 2010 Pearson Education, Inc.
Slide 6 - 4
Finding Normal Percentiles by Hand (cont.)

Table Z is the standard Normal table.

We have to convert our data to z-scores before using the
table
Copyright © 2010 Pearson Education, Inc.
Slide 6 - 5
Finding Normal Percentiles by Hand (cont.)
A table of Normal percentiles lets us find the percentage
of individuals in a Standard Normal distribution falling
below any specified z-score value.
(Table Z in Appendix G)
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Slide 6 - 6
Finding Normal Percentiles by Hand (cont.)
EXAMPLE:
Find the area to the left in the figure below we have a zscore of 1.8.
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Slide 6 - 7
DO THE MATH


Textbook page 125 # 8
Finish for homework
Copyright © 2010 Pearson Education, Inc.
Slide 6 - 8
Homework

Textbook page 132 #’s 26, 29, 30
Copyright © 2010 Pearson Education, Inc.
Slide 6 - 9