Lesson 2-4 Pages 69-72

Lesson 2-4 Pages 69-72

Mean, Median, and Mode

Lesson Check 2-3

What you will learn!

How to find the mean, median, and mode of a

set of data.

Measures of central tendencyMeasures of central tendency

MeanMean

ModeMode

MedianMedian

What you really need to know!

•The mean is the sum of the data divided by the number of data items.

•The median is the middle number of the ordered data, or the mean of the middle two numbers.

What you really need to know!

•The mode is the number (or numbers) that occur most often.

•The mean, median, and mode are each measures of central tendency.

Find the mean, median, and mode for each set of data!

1, 5, 9, 1, 2, 6, 8, 2

Mean = 4.25Median = 3.5Mode = 1 and 2

Find the mean, median, and mode for each set of data!

82, 79, 93, 91, 95, 95, 81

Mean = 88Median = 91Mode = 95

The line plot shows the number of children of U. S. presidents. Would the mean, median, or mode best represent the number of children?

Example 2:

0 1 2 3 4 5 6 7 8 9 10

xxxxxxx

xxxxxxx

xxxxx

xxxx

xxxx

xxxxxx

xxxxxx

xxx

xx

x x

There are 46 numbers. Add them together and divide the sum by 46.

7

5

11

4

6 6

32

1 1

0 1 2 3 4 5 6 7 8 9 10

xxxxxxx

xxxxxxx

xxxxx

xxxx

xxxx

xxxxxx

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xxx

xx

x x

143 ÷ 46 3.1 (mean)

0

5

22

12

24 30

1814

8 10

0 1 2 3 4 5 6 7 8 9 10

xxxxxxx

xxxxxxx

xxxxx

xxxx

xxxx

xxxxxx

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xxx

xx

x x

Since there are 46 numbers, the middle would be the 23rd number from the each end of the list. That would be a 2 and a 3. Take the mean of these two numbers to get the median.

0 1 2 3 4 5 6 7 8 9 10

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xxxxxxx

xxxxx

xxxx

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xxx

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x x

5 ÷ 2 = 2.5 (median)

0 1 2 3 4 5 6 7 8 9 10

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xxx

xx

x x

Median of 2.5 best represents

the data!

Mean = 3.1

Median = 2.5

Mode = 27

5

11

4

6 6

32

1 1

Extra:

When the numbers are all in the same neighborhood, the MEAN is the way to go! If there is one number out of the neighborhood, then the MEDIAN is the choice!

Page 71

Guided Practice

#’s 4-9

Pages 69-71 with someone at home

and study examples!

Read:

Homework: Page 72

#’s 10-16

#’s 20-27

Lesson Check 2-4

Page

568

Lesson 2-4

Lesson Check 2-4

Mid-Chapter Practice Test

Page

74

#’s 1-15

1. The number of pieces of data that fall within given intervals.

2. Example: Predicting profit earned by a company for the next year.

3. The greatest and least values, clusters of data, gaps in data, how the data is spread out, the range, and the mode (the most often number).

4. Sum of data divided by the number of terms in the data set.

Example 1:The table below shows the number of species of animals found at 30 major zoos across the U.S. Find the mean.

Number of Species in Major U.S. ZoosNumber of Species in Major U.S. Zoos

300300 400400 283283 400400 175175

617617 700700 700700 715715 280280

800800 290290 350350 133133 400400

195195 347347 488488 435435 640640

232232 350350 300300 300300 400400

705705 400400 800800 300300 659659

There are 30 numbers. Add them together and divide the sum by 30.

13,094

436.46÷ 30

Calculator

Example 2:

The table below shows the number of gold medals won by each country participating in the 2002 Winter Olympic games. Find the mean, median, and mode of the data.

2002 Winter Olympics: Gold Medals Won2002 Winter Olympics: Gold Medals Won

1212 66 44 33 00

1010 66 44 22 33

1111 22 33 44 22

11 11 00 22 22

11 00 00 00 00

There are 25 numbers. Add them together and divide the sum by 25.

79 = 3.16÷ 25

Example 2:

The table below shows the number of gold medals won by each country participating in the 2002 Winter Olympic games. Find the mean, median, and mode of the data.

2002 Winter Olympics: Gold Medals Won2002 Winter Olympics: Gold Medals Won

1212 66 44 33 00

1010 66 44 22 33

1111 22 33 44 22

11 11 00 22 22

11 00 00 00 00

0 0 0 0 0 0 1 1 1 2 2 2 2 2 3 3 3 4 4 4 6 6 10

11

12

2002 Winter Olympics: Gold Medals Won2002 Winter Olympics: Gold Medals Won

1212 44 33 22 00

1111 44 22 11 00

1010 44 22 11 00

66 33 22 11 00

66 33 22 00 00

Order the numbers from greatest to least. Find the number or numbers in the middle of the list.

2002 Winter Olympics: Gold Medals Won2002 Winter Olympics: Gold Medals Won

1212 44 33 22 00

1111 44 22 11 00

1010 44 22 11 00

66 33 22 11 00

66 33 22 00 00

The median for this data is 2.

2002 Winter Olympics: Gold Medals Won2002 Winter Olympics: Gold Medals Won

1212 44 33 22 00

1111 44 22 11 00

1010 44 22 11 00

66 33 22 11 00

66 33 22 00 00

The mode is the number or numbers that occur most often.The mode for this data is 0.

2002 Winter Olympics: Gold Medals Won2002 Winter Olympics: Gold Medals Won

1212 44 33 22 00

1111 44 22 11 00

1010 44 22 11 00

66 33 22 11 00

66 33 22 00 00