16-1

16-2 McGraw-Hill/Irwin © 2003 The McGraw-Hill Companies, Inc.,All Rights Reserved. Part Four ANALYSIS AND PRESENTATION OF DATA

16-3 Chapter Sixteen EXPLORING, DISPLAYING, AND EXAMINING DATA

16-4 Types of Data Analysis Exploratory data analysis –the data guide the choice of analysis--or a revision of the planned analysis Confirmatory data analysis –closer to classical statistical inference in its use of significance and confidence –may use information from a closely related data set or by validating findings through the gathering and analyzing of new data

16-5 Techniques to Display and Examine Distributions Frequency Table Visual Displays –Histograms –Stem-and-leaf display –Box-plot Crosstabulation of Variables

16-6 Techniques to Display and Examine Distributions Histograms –Display all intervals in a distribution, even without observed values –Examine the shape of the distribution for skewness, kurtosis, and the modal pattern

16-7 Techniques to Display and Examine Distributions (cont.) Box-plot (box and whisker-plot) –Rectangular plot encompasses 50% of the data values Edges of the box (hinges) –Center line through the width of the box marks the median –Whiskers extend from the right and left hinges to the largest and smallest values

16-8 Techniques to Display and Examine Distributions (cont.) Transformation –To improve interpretation and compatibility with other data sets –To enhance symmetry and stabilize spread –To improve linear relationships between and among variables

16-9 Improvement & Control Analysis Statistical process control –Uses statistical tools to analyze, monitor, and improve process performance –Total Quality Management –Control chart Displays sequential measurements of a process together with a center line and control limits –Upper control limit –Lower control limit

16-10 Types of Control Charts Variables data (ratio or interval measurements) –X-bar –R-charts –s-charts –Pareto Diagrams Bar chart whose percentages sum to 100 percent

16-11 Geographic Information Systems Systems of hardware, software, and procedures that capture, store, manipulate, integrate, and display spatially-referenced data

16-12 Geographic Information Systems Minimum four components –Integrating information from various sources –Capturing data –Projection and restructuring –Modeling

16-13 Crosstabulation A technique for comparing two classification variables –Cells –Marginals –Contingency tables

16-14 Percentaging Errors Averaging percentages without weighting Using too-large percentages (>100%) Using percentage with very small sample Citing percentage decrease exceeding 100 percent

16-15 Other Table-based Analysis Automatic Interaction Detection (AID) –Sequential partitioning procedure that uses a dependent variable and set of predictors –Searches among up to 300 variables for the best single division of data into subsets according to each predictor variable, –Chooses one division approach –Splits the sample using chi-square tests to create multi-way splits.