Variance and Standard Deviation.... a review of the notes.

What is the range in statistics?

• (Highest + lowest)/2

• Highest - lowest

• (Highest - lowest)/2

• (Highest - lowest)²

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CCSS.HSS.ID.A.3

What does variance represent?

• How many different variations are in the data set.

• How the population varies compared to the sample.

• How spread out each data value is from the mean.

• The range, but with a bunch of other stuff going on.

Before you can begin calculating the variance, you must first:

• find the mean

• find the median

• find the mode

• find the range

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CCSS.HSS.ID.A.2

CCSS.HSS.MD.A.2

Once you've calculated the mean, and listed the values in a table, what is the next step to calculating the variance?

• Square each value in the data set

• Subtract each value in the data set from the mean

• Subtract the mean from each value in the data set

• Add the mean to each value in the data set

After subtracting the mean from each value in the data set, the next step is to find the sum of those differences.

• True, then square that sum.

• False. Square the differences, then find the sum.

What is the difference between the formulas for population variance and sample variance?

• The sample variance is the square root of the population variance.

• The population variance divides the sum of the squares by n-1, while sample divides by N.

• The population variance divides the sum of the squares by N, while sample divides by n-1.

• There is no difference.

How do you calculate the standard deviation?

• Divide the variance by 2.

• Its a long process and I can't explain it right now.

• Find the mean and multiply it by the variance.

• Take the square root of the variance.

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CCSS.HSS.ID.A.4

Calculate the mean.

• μ = 10

• μ = 10.5

• x̄ = 10.5

• μ = 11

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CCSS.HSS.IC.B.4

CCSS.HSS.MD.A.2

CCSS.HSS.MD.A.3

Calculate the sum of the square of the difference.

(That is, steps 2, 3, and 4 ... Σ(x - μ)²

• 145.5

• 150

• 12

Last step... What is the variance?

• 24.25

• 29.1

• 2

• 4.9

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CCSS.HSS.ID.A.3

CCSS.HSS.ID.A.4