Jan. 23 Statistic for the Day: Average Number of Times an American Opens the Refrigerator Each Day:...

Jan. 23 Statistic for the Day:Average Number of Times an

American Opens the Refrigerator Each Day: 22

Assignment: Having read Chapter 9, Assignment: Having read Chapter 9, go back and study it closely.go back and study it closely.

Exercises p153-155: 1, 2, 4, 5, 9Exercises p153-155: 1, 2, 4, 5, 9

These slides were created by Tom Hettmansperger and in some cases modified by David Hunter

Source: Harper’s Magazine

Recall

Research Question or HypothesisResearch Question or Hypothesis QuantificationQuantification Collect dataCollect data Analyze dataAnalyze data Conclusions and/or actionConclusions and/or action

As first step in extracting information from data use graphics or pictures:

BoxplotBoxplot Stem and leafStem and leaf

Median and quartilesMedian and quartiles Histogram or normal curveHistogram or normal curve

Mean and standard deviationMean and standard deviation

Boxplot

stat100 PSUfootball

100

200

300

Weight

Overlapping Histograms

Stat100

PSU football

100 200 300

0

10

20

30

C68

Fre

que

ncy

Histogram with Normal Curve

100 150 200

0

10

20

Fre

quen

cy

Stat 100 Women: Weight

Scatter Plot for two measurements: RELATIONSHIP

100 200 300

100

200

300

weight

ide

al w

t

Stat 100 F01

US Pop and Violent CrimeTable 9.2 p155 text

YearYear 19821982 19831983 19851985 19861986 19871987 19881988 19891989 19901990 19911991

US PopUS Pop 231231 234234 239239 241241 243243 246246 248248 249249 252252

No. No. crimescrimes

1.321.32 1.261.26 1.331.33 1.491.49 1.481.48 1.571.57 1.651.65 1.821.82 1.911.91

In millions

250240230

8

7

6

5

4

3

2

1

0

pop

no./

10

00

If we want to suggest a much more dramatic increase:

250240230

7.5

6.5

5.5

pop

no./

10

00

Enrolment in higher educationAs percent of population

Moral of the story:

Whenever you meet a graph that is very far from square, it is likely to producean impression different from what you would have obtained from the data themselves.

Almost any graph in which the vertical scale does not start with zero is deceptive.

Another moral:

This Is a Good Bar GraphEarned Degrees 1976 in

thousands

0100200300400500600

MenWomen

BAD

• The problem with the pens is that it is the heights that should be compared.

• But instead, we end up comparing the areas.

• The areas do not make the correct comparison.

GOOD But with an error

•The letters are good because each letter represents an amount.

• However, one should use the correct number of letters

Bogus vertical scale. Hard to say what the graph should look like.

Portion of income taken by the government. Top: spending equal to the income in western states. Bottom: more densely populated east.

Some people think it means that rhinos have gotten smaller!