11

AverageA single number which FAIRLY represents a group of other numbers.

There are 3 types of average ( 3 different ways of working out an average number )

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22

MEAN

MEDIAN

MODE

Add up all the numbers and then divide by how many numbers there are.

Put the numbers in order of size and then find the middle number.

The number which appears most often.

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33Menu

44

MEAN

Add up all of the numbers and then divide by how many numbers there are.

Maths----- 72 %

English--- 56 %

History----60 %

French----55 %

Science-- 86 %

72

56

60

55

86

+

329329

5= 65.8 %

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55Menu

66

Median Median (Put in order of size then find the middle number)(Put in order of size then find the middle number)

44 22 77 88 11 1212 99

Median = 7Median = 7

1313

7 + 8 7 + 8

22= 7.5= 7.5

What if there is an even number

of numbers ?

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77

Another Method of Locating The Median From Raw Data

2, 3, 3, 3, 5, 7, 8, 9, 9, 11, 12, 14, 14, 15, 18

Firstly count how many numbers there are in the list.

15 Then ADD 1 and divide by 2+ 1

2= 16

2

= 8th number.

Now count to it.

Median = 9

What if there is an even number

of numbers ?

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88

What if there is an even number

of numbers ?

3, 5, 7, 11, 11, 13, 15, 21, 22, 23, 26, 30

Count how many numbers there are:

12Then ADD 1 and divide by 2

+ 12

= 13

2

= 6.5th number

Between the 6th & 7th numbers

Median = 14

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99Menu

1010

Mode (Modal Average)Mode (Modal Average)(The number/data which appears most often)(The number/data which appears most often)

Ex1) 3, 5, 2, 5, 3, 2, 4, 1, 3Ex1) 3, 5, 2, 5, 3, 2, 4, 1, 3 Ex2) 12, 14, 14, 15, 11, 15, 16, 10Ex2) 12, 14, 14, 15, 11, 15, 16, 10

Ex3) 1, 0, 2, 1, 0 ,2, 3, 3 Ex3) 1, 0, 2, 1, 0 ,2, 3, 3

Mode = 3Mode = 3

Mode = 14 & 15Mode = 14 & 15

No ModeNo Mode

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1111Menu

1212

So anybody with a small range must be clever ?

The RANGEHighest number – Lowest number

What does it show ?

Paul’s exam marks:

Maths 89%

Science 90%

English 90%

History 88%

French 91%

Range: 91- 88 = 3

David’s exam marks:

Maths

Science

English

History

French

Range = 3

?

?

?

?

?

4%

3%

6%

5%

4%

Small RangeConsistent

ReliablePredictable

David must be clever !Obviously

not !

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1313

Jane’s exam marks:

Maths 87%

Science 55%

History 32%

French 74%

English 45%

Range = 87 – 32 = 55

Big RangeInconsistentUnreliable

Unpredictable

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