Chapter 2.1（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 2.1 Frequency Distributions and Their Graphs 1 Copyright 2019, 2015, 2012, Pearson Education, Inc. Section 2.1 Objectives How to construct a frequency distribution including limits, midpoints, relative frequencies, cumulative frequencies, and boundaries How to construct frequency histograms, frequency polygons, relative frequency histograms, and ogives 1 Copyright 2019, 2015, 2012, Pearson Education, Inc. Frequency Distribution Frequency Distribution A table that shows classes or intervals of data with a count of the number of entries in each class. The frequency, f, of a class is the number of data entries in the class. Class Frequency, f 1 – 5 5 6 – 10 8 11 – 15 6 16 – 20 8 21 – 25 5 26 – 30 4 1 Copyright 2019, 2015, 2012, Pearson Education, Inc. Frequency Distribution Each class has a lower class limit, which is the least number that can belong to the class, and an upper class limit, which is the greatest number that can belong to the class. Class Frequency, f 1 – 5 5 6 – 10 8 11 – 15 6 16 – 20 8 21 – 25 5 26 – 30 4 Lower class limits Upper class limits 1 Copyright 2019, 2015, 2012, Pearson Education, Inc. Frequency Distribution The class width is the distance between lower (or upper) limits of consecutive classes. The difference between the maximum and minimum data entries is called the range. Class Frequency, f 1 – 5 5 6 – 10 8 11 – 15 6 16 – 20 8 21 – 25 5 26 – 30 4 Class width 6 – 1 = 5 1 Copyright 2019, 2015, 2012, Pearson Education, Inc. Constructing a Frequency Distribution Decide on the number of classes. Usually between 5 and 20; otherwise, it may be difficult to detect any