Displaying Data with Graphs

1
Displaying Data with Graphs

• Dot Plot
• Stemplot

2
Describing a Graph

• Center
• Shape
• Spread

3
Center

• If you had to pick a single number to describe
  all the data the center would be the best.
• Its in the middle!
• Median Half the numbers are larger half are
  smaller.
• Mean average of the numbers

4
Shape

• Are there any peaks?
• Mode occurs the most often.
• Is it skewed? Where is the tail?
• Skewed right the tail is to the right
• Skewed left the tail is to the left

5
Shape Are there modes?
Bimodal
Unimodal
How many bumps are in the graph? Those are
modes.
6
Uniform Dont appear to have any mode. All
bars are approximately the same height.
7
Symmetric?

• Can you fold it along a vertical line through
  the middle and have the edges math pretty
  closely? If so, then its symmetric.

8
Shape Skewed?

• Its skewed to the side of the longer tail.

Positively Skewed or (Skewed right)
Negatively Skewed or (Skewed left)
9
Shape Unusual Features

• Are there any stragglers, or outliers?
• Are there any gaps?

10
Spread (Variation)

• How spread out is the data?
• Range Difference between highest lowest
• How spread out is the interquartile range?
• IQR the middle 50
• Is it tightly clustered around the center or
  spread out?

11
We looked at the base salaries of the CEOs of the
800 largest corporations in 1994.

• Center Centered around 500,000
• Shape Unimodal, Nearly Symmetric, Some high
  outliers
• Spread Majority are between 100,000 and
  1,000,000. But there are a few with salaries
  between 2,500,000 and 3,000,000

12
Dotplots

• How many classes are you taking?

13
Homework

• Page 42 (37, 39, 41)