商务统计全英Chapter2.pptVIP

Price Range Colonial Log Split A-Frame $99,000 $99,000 60.00 30.00 54.29 80.00 40.00 70.00 45.71 20.00 Home Style 100 100 100 100 Total (Colonial and $99K)/(All Colonial) x 100 = (12/30) x 100 Crosstabulation: Column Percentages Crosstabulation: Simpson’s Paradox Simpson’ Paradox: In some cases the conclusions based upon an aggregated crosstabulation can be completely reversed if we look at the unaggregated data. We must be careful in drawing conclusions about the relationship between the two variables in the aggregated crosstabulation. Data in two or more crosstabulations are often aggregated to produce a summary crosstabulation. A useful way to visually display the results of cross -classification data is by constructing a side-by-side bat chart. The general pattern of the plotted points suggests the overall relationship between the variables. One variable is shown on the horizontal axis and the other variable is shown on the vertical axis. A scatter diagram is a graphical presentation of the relationship between two quantitative variables. Scatter Diagram and Trendline A trendline is an approximation of the relationship. A Positive Relationship x y Scatter Diagram and Trendline A Negative Relationship x y Scatter Diagram and Trendline No Apparent Relationship x y Scatter Diagram and Trendline Example: Panthers Football Team Scatter Diagram and Trendline The Panthers football team is interested in investigating the relationship, if any, between interceptions made and points scored. 1 3 2 1 3 14 24 18 17 30 x = Number of Interceptions y = Number of Points Scored y x Number of Interceptions Number of Points Scored 5 10 15 20 25 30 0 35 1 2 3 0 4 Scatter Diagram and Trendline Insights Gained from the Preceding Scatter Diagram The relationship is not perfect; all plotted points in the scatte