1. STATISTICS ELEMENTARY MARIO F. TRIOLA
Section Exploratory Data Analysis (EDA)
MARIO F. TRIOLA
EIGHTH
EDITION

2. Exploratory Data Analysis
The process of using statistical tools (such as graphs, measures of center, and measures of variation) to investigate the data sets in order to understand their important characteristics
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3. Outliers
a value located very far away from almost all of the other values
an extreme value
can have a dramatic effect on the mean, standard deviation, and on the scale of the histogram so that the true nature of the distribution is totally obscured
Outliers can have a dramatic effect on the certain descriptive statistics (mean and standard deviation). It is important to be aware of such data values.

4. Boxplots (Box-and-Whisker Diagram)
Reveals the:
center of the data
spread of the data
distribution of the data
presence of outliers
Excellent for comparing two or more data sets
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5. Boxplots 5 - number summary Minimum first quartile Q1 Median (Q2)
third quartile Q3
Maximum
Medians and quartiles are not very sensitive to extreme values.
Refer to Section 2-6 for finding the Q1 and Q3 values, and Section 2-4 for finding the median.

6. Boxplots 2 4 6 14
It appears that the Qwerty data set has a skewed right distribution
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Figure Boxplot of Qwerty Word Ratings

7. Bell-Shaped Figure 2-19 Boxplots
A bell-shaped boxplot should have approximately the same distance from minimum to Q1 as Q3 to maximum.
Also the same distance should also occur from Q2 to the median as from the median to Q3.
Bell-Shaped

8. Bell-Shaped Uniform Figure 2-19 Boxplots
A uniform boxplot should have approximately the same distance from minimum to Q1, Q1 to Q3, Q3 to maximum.
Bell-Shaped
Uniform

9. Figure Boxplots
Bell-Shaped
Uniform
Skewed

10. Exploring Measures of center: mean, median, and mode
Measures of variation: Standard deviation and range
Measures of spread and relative location:    minimum values, maximum value, and quartiles
Unusual values: outliers
Distribution: histograms, stem-leaf plots, and boxplots
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