《统计学基础（英文版·第7版）》课件les7e_ppt_ADA_0203.pptxVIP

Elementary StatisticsChapter 2Seventh EditionDescriptive StatisticsCopyright 2019, 2015, 2012, Pearson Education, Inc.Chapter Outline2.1 Frequency Distributions and Their Graphs2.2 More Graphs and Displays2.3 Measures of Central Tendency2.4 Measures of Variation2.5 Measures of PositionSection 2.3Measures of Central TendencySection 2.3 ObjectivesHow to find the mean, median, and mode of a population and of a sampleHow to find the weighted mean of a data set, and how to estimate the sample mean of grouped dataHow to describe the shape of a distribution as symmetric, uniform, or skewed and how to compare the mean and median for eachMeasures of Central TendencyMeasure of central tendencyA value that represents a typical, or central, entry of a data set.Most common measures of central tendency:MeanMedianModeMeasure of Central Tendency: MeanMean (average)The sum of all the data entries divided by the number of entries.Sigma notation: in the data set.Population mean: Sample mean: Example: Finding a Sample MeanThe weights (in pounds) for a sample of adults before starting a weight-loss study are listed. What is the mean weight of the adults?274 235 223 268 290 285 235Solution: Finding a Sample Mean274 235 223 268 290 285 235The sum of the weights is To find the mean weight, divide the sum of the weights by the number of adults in the sample.The mean weight of the adults is about 258.6 pounds.Measure of Central Tendency: MedianMedianThe value that lies in the middle of the data when the data set is ordered.Measures the center of an ordered data set by dividing it into two equal parts.If the data set has anodd number of entries: median is the middle data entry.even number of entries: median is the mean of the two middle data entries.Example: Finding the Median (1 of 2)Find the median of the weight listed in the first example.274 235 223 268 290 285 235Solution: Finding the Median (1 of 2)First, order the data.223 235 235 268 274 285 290There are seven entries (an odd number),