Chapter 3 section 3: Mean, Median, and Mode

Tuesday, November 08, 2011Instructor: Mr. Johnson

New Vocabulary

Mean (Average): The sum of the data items divided by the number of data items.

Median: The middle number when data items are written in order and there is an odd number of data items.

Mode: The data item that occurs most often. There can be more than one mode.

Outlier: A data value that is much higher or lower than the other data values.

Finding the Mean

Mean =

Example: Find the mean of the following: 50,48,55,42,39,44,53

Sum of data items: 50+48+55+42+39+44+53= 331

The number of data items: 7

Sooo…. Our mean would be

Sum of data items

The number of data items

331

7= 47.3

Finding the Median

Median- The middle number when data items are written in order and there is an odd number of data items. For an even number of data items, the median is the mean of the two middle numbers.

Example- Find the Median of the following: 50,48,55,42,39,44,53

First we must put them in order from least to greatest: 39, 42,44, 48, 50, 53, 55

The median is…..48

Example with an even number of data items: 39, 42,44, 48, 50, 53

44+48

2= 46

Finding the Mode

Mode: The data item that occurs most often. There can be more than one mode.

Example: Find the mode of the following: 39, 44, 55, 35, 44, 41, 34, 56, 44

The mode is…..44

Outliers

Outlier: A data value that is much higher or lower than the other data values . An outlier can affect the mean of a group of data.

Find an outlier in the group of data and tell how it affects the mean: 9, 10, 12, 13, 8, 9, 31, 9

The outlier would be….31

To find how it affects the mean, we must calculate the mean both with and without the outlier.

With: Without:

The outlier raises the mean by 2.6

9+10+12+13+8+9+31+9

8= 12.6

9+10+12+13+8+9+9

7= 10

Example

Seven elementary students are participating in a one-week Readathon to raise money for a good cause. These are the number of pages read by each student 40, 45, 48, 50, 50, 59, 20.

Find the mean, median, and mode. Identify the outlier and tell how it affects the mean.

Answers

Mean: 44.6Median: 48Mode: 50Outlier: 20, It decreases the mean by

4.1

Homework!!!!!

In the first ten games of this season the LA Lakers scored 98, 89, 95, 102,98, 105, 89, 91, 98, 105

Find the mean, median, and mode of the scores for their first 10 games