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Central Tendency 4-4 Mean The average of the data Steps to take to find the average ◦ 1. Add all numbers together ◦ 2. Divide that answer by how many numbers there were in the original Example Word Problem Randy Johnson manages a fast-food restaurant called Shelley’s. The head office wants to know the average length of employment at the restaurant. Randy compares the starting date and ending date for every employee who left during the last 6 months. Here is the number of months that each of those employees worked at Shelley’s: Ashley – 6, Joey – 14, Mike – 8, Lisa – 3, Nick – 12, Annie – 9, Bobby – 15, Tom – 18, Denise - 14 Step 1 – Add all numbers together ◦ 6 + 14 + 8 + 3 + 12 + 9 + 15 + 18 + 14 = 99 Step 2 – Divide by the amount of numbers you had ◦ 99 ÷ 9 = ◦ 11 ◦ So the average length of employment at Shelley’s restaurant was 11 months. Examples 1. 10, 6, 9, 14, 11 2. 5, 9, 3, 12, 6, 17 Median Gives the middle value when the numbers are listed in order ◦ 1. put the numbers in order from least to greatest ◦ 2. find the number in the middle ◦ 3. (if there are two numbers in the middle, add them and divide by two) Examples: 26, 15, 48, 53, 74, 39 4, 6, 10, 11, 6, 2, 6, 3 Mode Value the occurs most often ◦ 1. find the number that is repeated the most ◦ 2. if no numbers are repeated, there is NO MODE ◦ 3. if there are multiple numbers that are repeated the same amount of times, they both/all are the mode Examples: 1. 46, 3, 57, 89, 2, 17, 101, 33 2. 19.4, 89.6, 75.34, 19.4, 0.01, 89.6 Range Shows how much the data varies and is the difference between the greatest number and the least number ◦ 1. take the biggest # and subtract the smallest # Examples: 1. 45, 79, 21, 86, 55, 94 2. 4, 6, 10, 11, 6, 2, 6, 3 Outlier The outlier is a data value that is much greater or much less than the other data values An outlier WILL affect the mean of a group of data Ex. 4, 3, 7, 29, 2, 5 The outlier is 29 because it is much bigger than the rest of the numbers