7th Grade Math Mean, Median, and Range Obj. 5b

Central Tendency Mean Median Set of Numbers: 2, 3, 1, 1, 0, 1, 2, 4 When you have a “set of data” (or numbers), there are 2 different ways you can find the center of the data. Mean Median Let’s look at these 2 different ways to find the center using the following… Set of Numbers: 2, 3, 1, 1, 0, 1, 2, 4

Mean Mean = Average

Divide by the # of items in the dataset. What is the Mean? Your report card has an average on it. The Mean is the average. 2 simple steps will give you the mean of a set of numbers. Mean = Average Step 1 Add the numbers. Step 2 Divide by the # of items in the dataset.

Divide by the # of items in the dataset. Example of Mean: Step 1 Add the numbers. Step 2 Divide by the # of items in the dataset. Set of Numbers: 2, 3, 1, 1, 0, 1, 2, 4 Add the numbers: 2 + 3 + 1 + 1 + 0 + 1 + 2 + 4 = Divide by total items: 14 ÷ 8 = Mean 14 1.75

Median Median = Middle

What is the Median? The Median is the middle number. How do you find the Median? Median = Middle If there is just 1 middle #: your done! ORDER the numbers. FIND the middle #. If there are 2 middle #’s Average the 2 middle numbers.

Example of Median Median Set of Numbers: 2, 3, 1, 1, 0, 1, 2, 4 ORDER the numbers. If there is just 1 middle #: your done! If there are 2 middle #’s FIND the middle #. Average the 2 middle numbers. Add the 2 middle numbers Then, Divide by 2 Set of Numbers: 2, 3, 1, 1, 0, 1, 2, 4 Arrange in order: 0, 1, 1, 1, 2, 2, 3, 4 1 + 2 = 3 3 ÷ 2 = 1.5 Median

Range Range = Biggest – Smallest

What is the Range? Range = Biggest - Smallest The Range is not a form of central tendency, but it is another way to get information from a “set of numbers”. The range describes the spread of the dataset. The Range is the difference between the biggest number and the smallest number. Range = Biggest - Smallest Temperature Range Michigan: 35 degrees Florida: 75 degrees Temperature Range was 40 degrees!

Example of Range 4 Range = Biggest – Smallest Set of Numbers: 2, 3, 1, 1, 0, 1, 2, 4 Subtract: 4 – 0 = 4 Range

Remember.... Average Mean = Median = Range = Middle Biggest – Smallest

You Try! Mandy’s math test scores: 90, 85, 80, 70, 90, 65 90, 85, 80, 70, 90, 65 Determine the following: Mean _______ Median _______ Range _______

Answers! Mandy’s math test scores: 90, 85, 80, 70, 90, 65 90, 85, 80, 70, 90, 65 65 70 80 85 90 90 Mean __80___ Median __82.5_ (find average of 80 & 85) Range __25___ Order the numbers. Mean : Add numbers: 480 Divide by : 6 Answer: 480 ÷ 6 = 80 So, Mean = 80 Median: There are two numbers in the middle. Average: 80 + 85 = 165 ÷ 2 So, Median = 82.5 Mode: 90 occurs the most So, Mode = 90 Range: 90 – 65 = 25 So, Range = 65

Closure What did we learn today (key words): Mean = _________________ ? Median = _________________ ? Range = _________________ ? Which central tendency requires you to first put the numbers in order? When finding the median, what do you do if there are 2 middle numbers? Average Middle Most Biggest – Smallest Median Average the two middle numbers by adding them together and dividing by 2.