Measures of Variability for Grouped Data

Mean, Variance and Standard Deviation Lesson

Elizabeth Borres

At the end of the lesson, students should be able to:

1. Find the mean for grouped data.

2. Calculate the variance and standard deviation.

3. Apply the measures of variability in real life.

Multiple Choice

If we are using the Median as the Measure of Center, which Measure of Variability should we use to best represent the data?

• IQR

• MAD

Multiple Choice

If we are using the Mean as the Measure of Center, which Measure of Variability should we use to best represent the data?

• IQR

• MAD

Multiple Select

The two Measure of Variability we have study this unit are...

• Mean

• Median

• IQR

• MAD

Multiple Choice

In order to find the median, the data must be sorted from least to greatest first.

• True

• False

Multiple Choice

What is the third quartile?

• 4

• 5

• 6

• 7

Multiple Choice

What is the first quartile?

• 4

• 5

• 6

• 7

Multiple Choice

What is the range?

• 6

• 2 - 8

• 3

• 4

Poll

Do you have any questions/clarifications?

What is Variance?

• It is the average squared deviation from the mean of the set of dat.

• It is used to find the standard deviation.

How to find the Variance?

• Find the mean of the data.

• Subtract the mean from each value. The result is called the deviation from the mean.

• Square each deviation from the mean.

• Find the sum of the squares.

• Divide the total by the number of items. This is the total frequency (N).

Open Ended

Journal: Explain how to find the sample variance?