Statistics
February 4, 2008
Outline
1. Describing range and center via boxplots
2. quartiles (hinges), IQR, outliers (1.5 IQR rule)
3. relationships between two variables
4. side-by-side boxplots
5. formulas in R
Homework - due Thursday, February 8
1. Read pages 117–119 and Appendix A.7.
2. Do problems 1.14,15
Useful R
> bwplot(count~spray,data=InsectSprays)
Miscellaneous notes
Egregious typo in problem A.3: displayed formula should be
median{|x1 − m|, . . . , |xn − m|}
Notation from last class: If x1 , . . . , xn are the values of variable x on the n individuals in the
dataset, then x(1) , . . . , x(n) are these same values but reordered so that x(1) ≤ x(2) ≤ · · · ≤ x(n−1) ≤
x(n) .
The insect spray data comes from this table in an article by Beall. The insect is commonly
known as the tomato hornworm and the five-spotted hawkmoth.