1. Algebra 1: Section 2-7 Using Measures of Central Tendency

2. Important Terms: Measures of Central Tendency include: Mean, Median, and Mode. Mean = Sum of items divided by total number of items (also called the “average”) Outlier: a data value that is much higher or lower than the other data values in the set. Median: the middle value in the set when the numbers are arranged in order. For an even number of data items, take the two middle items and find the average of the two. Mode: data item that occurs the most times. Possible to have no mode, one mode, or more than one mode.

3. Important Terms Range: the difference between the greatest and least data values Stem and Leaf Plot: a display of data made by using the digits of the values.

4. When to Use… Use the MEAN to describe the middle of a set of data that does not have an outlier. Use the MEDIAN to describe the middle of a set of data that does have an outlier. Use the MODE when the data are nonnumeric or when choosing the most popular item.

5. Examples: Find the mean, median, and mode. Which measure of central tendency best describes the data? Ages of students on the math team: 14, 14, 15, 15, 16, 15, 15, 16 Given the following test grades, what do you need to make on the next test to have a 91 average? –99, 86, 76, 95

6. Examples: Find the range. –5.3, 6.2, 3.1, 4.8, 7.3 Make a stem-and-leaf plot for the data. –4.5, 4.3, 0.8, 3.5,2.6, 1.4, 0.2, 0.8, 4.3, 6.0

7. Example: CityHighway 91 9 8 3 3 027878 4 1 130 2 2 7 8 8 41 a. Find the Mean of the City Mileage and the Highway Mileage. b. Find the Median of the City and Highway Mileage c. Find the mode(s) of the city mileage and of the highway mileage d.Find the range of the city mileage and of the highway mileage

8. Assignment: Pg. 121: multiples of 3 #3-24, 25, 27, 28,