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Section 2.2, Part 2 Determining Normality AP Statistics

Section 2.2, Part 2 Determining Normality AP Statistics

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Page 1: Section 2.2, Part 2 Determining Normality AP Statistics

Section 2.2, Part 2Determining Normality

AP Statistics

Page 2: Section 2.2, Part 2 Determining Normality AP Statistics

AP Statistics, Section 2.2, Part 2 2

What is “Normal”?

Because we should only apply z-score to distributions that are normal, we need a process to determine whether a distribution is a normal distribution.

Page 3: Section 2.2, Part 2 Determining Normality AP Statistics

AP Statistics, Section 2.2, Part 2 3

Symmetric?

The distribution should be roughly symmetric.

You can use a Boxplot to determine symmetry.

Page 4: Section 2.2, Part 2 Determining Normality AP Statistics

AP Statistics, Section 2.2, Part 2 4

Are Walter Johnson’s Wins Normal? 5, 14, 13, 25, 25, 33,

36, 28, 27, 25, 23, 23, 20, 8, 17, 15, 17, 23, 20, 15, 5 into list L1

Run “1-Var Stats” Is the data set

symmetric? Where do you look?

Page 5: Section 2.2, Part 2 Determining Normality AP Statistics

AP Statistics, Section 2.2, Part 2 5

Are Walter Johnson’s Wins Normal? Look also at boxplot Is the data set

symmetric?

Page 6: Section 2.2, Part 2 Determining Normality AP Statistics

AP Statistics, Section 2.2, Part 2 6

68-95-99.7 Rule?

You can use the 68-95-99.7 rule with a histogram to see if the distribution roughly fits the rule.

Page 7: Section 2.2, Part 2 Determining Normality AP Statistics

AP Statistics, Section 2.2, Part 2 7

Are Walter Johnson’s Wins Normal? 5, 5, 8, 13, 14, 15, 15, 17,

17, 20, 20, 23, 23, 23, 25, 25, 25, 27, 28, 33, 36

Page 8: Section 2.2, Part 2 Determining Normality AP Statistics

AP Statistics, Section 2.2, Part 2 8

Are Walter Johnson’s Wins Normal? Last step is the creation of the “normal

probability plots Let’s look at the book example:

Page 9: Section 2.2, Part 2 Determining Normality AP Statistics

AP Statistics, Section 2.2, Part 2 9

Example 2.12

X Midpoint Y

1 1/8=.1250 -1.15

2 3/8=.3750 -.319

2 5/8=.6250 .319

3 7/8=.8750 1.15

Page 10: Section 2.2, Part 2 Determining Normality AP Statistics

AP Statistics, Section 2.2, Part 2 10

Example 2.12

X Midpoint Y

1 1/8=.1250 -1.15

2 3/8=.3750 -.319

2 5/8=.6250 .319

3 7/8=.8750 1.15

Page 11: Section 2.2, Part 2 Determining Normality AP Statistics

AP Statistics, Section 2.2, Part 2 11

Example 2.12

X Midpoint Y

1 1/8=.1250 -1.15

2 3/8=.3750 -.319

2 5/8=.6250 .319

3 7/8=.8750 1.15

Page 12: Section 2.2, Part 2 Determining Normality AP Statistics

AP Statistics, Section 2.2, Part 2 12

Somewhat normal (somewhat linear)

Page 13: Section 2.2, Part 2 Determining Normality AP Statistics

AP Statistics, Section 2.2, Part 2 13

Example 2.12

X Midpoint Y

1 1/10=.1 -1.282

2 3/10=.3 -0.524

2 5/10=.5 0.000

3 7/10=.7 0.524

10 9/10=.9 1.282

Page 14: Section 2.2, Part 2 Determining Normality AP Statistics

AP Statistics, Section 2.2, Part 2 14

Example 2.12

X Midpoint Y

1 1/10=.1 -1.282

2 3/10=.3 -0.524

2 5/10=.5 0.000

3 7/10=.7 0.524

10 9/10=.9 1.282

Page 15: Section 2.2, Part 2 Determining Normality AP Statistics

AP Statistics, Section 2.2, Part 2 15

Example 2.12

X Midpoint Y

1 1/10=.1 -1.282

2 3/10=.3 -0.524

2 5/10=.5 0.000

3 7/10=.7 0.524

10 9/10=.9 1.282

Page 16: Section 2.2, Part 2 Determining Normality AP Statistics

AP Statistics, Section 2.2, Part 2 16

Not normal (not linear)

Page 17: Section 2.2, Part 2 Determining Normality AP Statistics

AP Statistics, Section 2.2, Part 2 17

Walter Johnston Normal?

Page 18: Section 2.2, Part 2 Determining Normality AP Statistics

AP Statistics, Section 2.2, Part 2 18

Assignment

Exercises 2.26 – 2.31, 2.33, 2.36 to finish Section 2.2

Exercises 2.39, 2.40, 2.42, 2.45, 2.47 to finish Chapter 2