Measure of Variability - Variance

Measure of Variability - Variance

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Multiple Choice

The difference between the highest and the lowest score is _______________________________.

• range

• standard deviation

• variance

• average deviation

Multiple Choice

How do you find the range of a set of numbers?

• Subtract the largest number from the smallest number

• It is the number that occurs most often

• Add all the numbers and divide by how many numbers there are

• Subtract the smallest number from the largest number

Fill in the Blank

What is the range?

Fill in the Blank

What is the range?

Fill in the Blank

What is the range?

Steps for finding variance

Write each step involved in finding the variance carefully.

​Find the variance of 10, 60, 50, 30, 40, 20

1st step: Find the mean

Multiple Choice

​Find the variance of 10, 60, 50, 30, 40, 20

1st step: Find the mean

• 30

• 35

• 40

• 45

​​Find the variance of 10, 60, 50, 30, 40, 20

1st step: Find the mean=35

2nd step: Find the deviation from the mean

​​​Find the variance of 10, 60, 50, 30, 40, 20

1st step: Find the mean=35

2nd step: Find the deviation from the mean

10-35=-25

60-35=25

50-35=15

30-35=-5

40-35=5

20-35=-15

​​​​Find the variance of 10, 60, 50, 30, 40, 20

1st step: Find the mean=35

2nd step: Find the deviation from the mean 3rd step: Square each deviation

10-35=-25 (-25)^2=625

60-35=25 25^2=625

50-35=15 15^2=225

30-35=-5 (-5)^2=25

40-35=5 5^2=25

20-35=-15 (-15)^2=225

​​​​​Find the variance of 10, 60, 50, 30, 40, 20

1st step: Find the mean=35

2nd step: Find the deviation from the mean 3rd step: Square each deviation

10-35=-25 (-25)^2=625

60-35=25 25^2=625

50-35=15 15^2=225

30-35=-5 (-5)^2=25

40-35=5 5^2=25

20-35=-15 (-15)^2=225

4th step: Find the sum of all the squares

625+625+225+25+25+225

1,750

​Find the variance of 10, 60, 50, 30, 40, 20

1st step: Find the mean=35

2nd step: Find the deviation from the mean 3rd step: Square each deviation

10-35=-25 (-25)^2=625

60-35=25 25^2=625

50-35=15 15^2=225

30-35=-5 (-5)^2=25

40-35=5 5^2=25

20-35=-15 (-15)^2=225

4th step: Find the sum of all the squares

625+625+225+25+25+225=1,750

5th step: Divide the sum by n-1

1,750/5=350