Chapter 2.4（课件）- 《统计学基础（英文版）》同步教学（人民大学版）

Chapter Descriptive Statistics 2 1 Copyright 2019, 2015, 2012, Pearson Education, Inc. 1 Larson/Farber 6th ed Chapter 1 Chapter Outline 2.1 Frequency Distributions and Their Graphs 2.2 More Graphs and Displays 2.3 Measures of Central Tendency 2.4 Measures of Variation 2.5 Measures of Position 1 Copyright 2019, 2015, 2012, Pearson Education, Inc. Section 2.4 Measures of Variation . 1 Copyright 2019, 2015, 2012, Pearson Education, Inc. Section 2.4 Objectives How to find the range of a data set How to find the variance and standard deviation of a population and of a sample How to use the Empirical Rule and Chebychev’s Theorem to interpret standard deviation How to approximate the sample standard deviation for grouped data How to use the coefficient of variation to compare variation in different data sets . 1 Copyright 2019, 2015, 2012, Pearson Education, Inc. Range Range The difference between the maximum and minimum data entries in the set. The data must be quantitative. Range = (Max. data entry) – (Min. data entry) . 1 Copyright 2019, 2015, 2012, Pearson Education, Inc. Example: Finding the Range Two corporations each hired 10 graduates. The starting salaries for each graduate are shown. Find the range of the starting salaries for Corporation A. . 1 Copyright 2019, 2015, 2012, Pearson Education, Inc. Solution: Finding the Range Ordering the data helps to find the least and greatest salaries. 37 38 39 41 41 41 42 44 45 47 Range = (Max. salary) – (Min. salary) = 47 – 37 = 10 The range of starting salaries for Corporation A is 10, or $10,000. minimum maximum . 1 Copyright 2019, 2015, 2012, Pearson Education, Inc. Variation Both data sets in the last example have a mean of 41.5, or $41,500, a median of 41, or $41,000, and a mode of 41, or $41,000. And yet the two sets differ significantly. The difference is that the entries in the second set have greater variation. As you can see in the figures on the next slide, the start