Statistics, Graphs and Examples

What you need to support your

“must knows”

Measures of Central Tendency

• Mean: Average; sum divided by number of measurements in a data set

• Median: Middle number in a data set

• Mode: Most frequently occurring number in a data set

X-Y Scatterplot

• Graph used to determine the relationship between two variables

• Relationship may be positive, negative or non-existent

• Correlation does not mean causation!!!

Year 2000 - Burlington VTRelationship Between Snowfall and

Temperature

0

10

20

30

40

0 20 40 60 80

Temperature in degrees F

Snow

fall

in in

ches

Bar Graph

• Histogram

• Graph used to show frequencies on the Y axis and characteristics on the X axis

• Used for discrete data

Suspected Nuclear Weapons

1550015000

482 410 200 100 60 200

2000

4000

6000

8000

10000

12000

14000

16000

18000

Source: Center for Defense Information

Line Graph

• Graph used to plot continuous data over time

• X axis contains timeline, Y axis shows frequencies

NYC Handwashing 1992- 1997

0

5

10

15

20

25

30

35

40

1992 1993 1994 1995 1996 1997

Per

cent

age

was

ing

hand

s

Pie Chart

• Graph used to show percentage of a meaningful whole

American Car Colors Year 2000

18%

17%

11%9%9%7%

29%

Silver

White

Black

Green

Blue

Red

Other

Source: Dupont Auto Color Survey

According to the Experts...

• Fonts with serifs are easier to read in print• Fonts sans serif are easier to read when

projected

Read Carefully...

• Random is not the same as a sample

• Be suspicious of research sponsored by a product supplier

• Celebrities often know little about their causes

In general…

• Use data from careful research and sampling polls

• Telling stories is useful to provide a personal touch

• It’s OK to give Personal opinion• Use Internet research from a credible site• Journals are preferable to popular periodicals

And, don’t forget...

• Know your subject

• Know your audience