1. Chapter Sixteen EXPLORING, DISPLAYING, AND EXAMINING DATA

2. Types of Data Analysis Exploratory data analysis:
finding clues and evidence
emphasis on visual representations and graphical techniques
guides the choice of analysis or a revision of the planned analysis

3. Types of Data Analysis Confirmatory data analysis
evaluating the strength of evidence
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

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

5. 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
Stem and Leaf Displays
Reveals the distribution of values within the interval and preserves their rank order

6. 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 are called “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

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

8. Control Charts
Displays sequential measurements of a process together with a center line and control limits (upper and lower)
Types for variables data (ratio or interval)
X-bar
R-charts
s-charts (sample standard deviation)
Pareto Diagrams (Bar chart whose percentages sum to 100 percent)

9. Geographic Information Systems
Systems of hardware, software, and procedures that capture, store, manipulate, integrate, and display spatially-referenced data (e.g. MapQuest)
Integrating information from various sources
Capturing data
Projection and restructuring
Modeling ( of best route)

10. Crosstabulation A technique for comparing two classification variables
Cells
Marginals
Contingency tables
A technique to test whether there is a difference between observed frequencies and expected frequencies

11. 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.