1. The Basic Practice of Statistics
David S. Moore
The Basic Practice of Statistics
Fourth Edition
Chapter 1:
Picturing Distributions with Graphs
Copyright © 2007 by W. H. Freeman & Company

2. Statistics – The study of how to collect, organize, analyze and interpret numerical information from data for the purpose of making decisions.

4. Important aspects of any graphical representation are
Shape, Center, Spread.

6. Graphs such as bar charts or pie charts help display the distribution of a variable

7. Dot plots
Does not have to begin at zero.
Should cover the range of values.

8. Groups data into classes.
Histogram
Classes
15<
% adults with bachelors degree
< 20
20< “
<25
25<
<30
30<
<35
35<
<40
40<
<45
Groups data into classes.
You can choose classes but must do so carefully.

10. symmetric
Skewed right

11. Used for small data sets.
Presents more detail.
All data is displayed

15. Measurements of Center

17. The mean is nonresistant (changed) to extreme observations or outliers; while the median is resistant (not changed).
Mean
Median
Mean and median are the same

18. Measuring Spread Range Measuring center alone can be misleading.
Often the spread or variability of the data is very important.
Range
The difference between the largest and smallest observations.

19. Example:
odd # of Observations Q3 Q1 M
even # of Observations Q1
14.5 Q3

24. Properties of Standard deviation
measures spread about the mean. Should only be used when the mean is the measure of center.
s = 0; only when there is no spread, all observations are exactly the same.
s is large; values are very spread out.
s is small; values are clustered close to the mean.
s is nonresistant likex (mean); strongly influenced by extreme observations or outliers.