8 1. Summarizing Data Sepal.Length 0 20 40 60 80 100 4 5 6 7 8 S.Width S.Width 4 5 6 7 8 S.Width S.Width 4 5 6 7 8 S.Width S.Width S.Width S.Width S.Width S.Width S.Width 0 20 40 60 80 100 S.Width 0 20 40 60 80 100 S.Width S.Width S.Width S.Width S.Width S.Width S.Width 4 5 6 7 8 S.Width S.Width 4 5 6 7 8 S.Width 0 20 40 60 80 100 S.Width Sepal.Length 0 10 20 30 4 5 6 7 8 Sepal.Width Sepal.Width Sepal.Width 4 5 6 7 8 0 10 20 30 Sepal.Width Figure 1.4. The output of histogram(∼Sepal.Length|Sepal.Width,iris) and histogram(∼Sepal.Length|equal.count(Sepal.Width,number=4),iris). x 0 5 10 15 20 0 5 10 15 neg. skewed 0 5 10 15 pos. skewed 0 5 10 15 symmetric eruptions 0 2 4 6 8 10 12 2 3 4 5 Figure 1.5. Left: Skewed and symmetric distributions. Right: Old Faithful eruption times illustrate a bimodal distribution. the degree and direction of skewness with a number for now it is suﬃcient to describe distributions qualitatively as symmetric or skewed. See Figure 1.5 for some examples of symmetric and skewed distributions. Notice that each of these distributions is clustered around a center where most of the values are located. We say that such distributions are unimodal. Shortly we Percent of Total Percent of Total Percent of Total Percent of Total

Purchased from American Mathematical Society for the exclusive use of nofirst nolast (email unknown) Copyright 2011 American Mathematical Society. Duplication prohibited. Please report unauthorized use to cust-serv@ams.org. Thank You! Your purchase supports the AMS' mission, programs, and services for the mathematical community.