Stemplots and Dotplots

LESSON 1.2

Stem and Leaf Plots

A kind of display that shows data in a structured form.

**To construct,Leaf: first digit on the rightStem: the remaining digit or digits

624

stem leaf

41, 26, 27, 33, 18, 27, 30, 31, 31, 33, 6, 41, 40, 28, 39, 29, 40, 9, 40, 8

Example

1

leaf

0

stem

2

3

4

6, 8, 9

8

6, 7, 7, 8, 9

0,1, 1, 3, 3, 9

0, 0, 0, 1, 1

Key: 1|8 means 18

The ages of the Wimbleton tennis champions in the men’s and women’s singles from 1970 to 1990 are shown below. The dot (*) between two stems breaks the stem into two parts (ie. 20-24, 25-29).

Find the range of ages for the men and the women.

Are there any outliers? If so, what are their ages?

*

Women

1

2

*

3

9,9,9

0,1,1,2

5,6,6,7,7,8,8,8,9,9

0,1,1,3

Key: 1|8 means 18

Men

*

8,7

4,4,4,3,2,2,2,2,1,1,1

9,7,7,6,5,5

1

14

No!

Pets that each student has in a classroom

0 1 2 3 4*How many students are in the class?

*What’s the frequency of students having 3 pets?

*What is the mean?

14

4

1.6

LESSON 1.3

Measures of Center

Definitions

Summation Notation: called “Sigma Notation”

The sum of f sub i’s as i goes from 3 to 8.

Mean:

Example 1

3

Height in inches

1

# of players

3

2

2

67

69

70

71

72

1

1

74

79

a. How many members does the team have?

a. Find the mean height?

b. Find the median height?

a. Which number best describes the typical height of a member of the team? Why?

13

71

70

The median – the mean is skewed because of 79.

Example 2

A class has 20 students. Let g1 = the test grade of the ith student.

A. Use ∑ notation to express the total of the test grades for the class.

B. What does represent?

The mean of the test scores.

Homework

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