Lesson 29/4/12

Lesson 2

Do Now:

Represent this data graphically

9/4/12

SiblingsErika 1

Samuel 2Ryan 2Nicky 0

Tia 1

Pop. Home Town

Erika 1,200,000Samuel 5,000Ryan 5,000Nicky 20,000,000

Tia 8,000

Homework:Read chapters 2 and 3Answer CIRCLED questions on hand-out:They are on pg.38-40 of book, #6,8,13,18,22,24

Frequency TableA Frequency Table

organizes counts (data) by providing totals and category names.

A bar chart displays the distribution of a categorical variable, showing the counts for each category next to each other for easy comparison Sam Erika Tia Ryan Nicky

0

5

10

15

20

25

Pairs of Shoes

Pairs of Shoes

Name Pairs of Shoes

Sam 4

Erika 16

Tia 12

Ryan 6

Nicky 21

Relative Frequency Table

A relative frequency table displays the percentages, rather than the counts, of the values in each category.

Name Pairs of Shoes

Sam 4

Erika 16

Tia 12

Ryan 6

Nicky 21

Name Pairs of Shoes % Total Shoes

Sam 4 6.78%

Erika 16 27.12%

Tia 12 20.34%

Ryan 6 10.17%

Nicky 21 35.59%

Sam Erika Tia Ryan Nicky0.00%

5.00%

10.00%

15.00%

20.00%

25.00%

30.00%

35.00%

40.00%

% Total Shoes

% Total Shoes

Pie ChartsTitanic PassengersPie charts show the

whole group of cases as a circle

How easy is it to tell there are almost twice as many third-class passengers as first class passengers?

Crew; 885

Third Class; 706

Second Class; 285

First Class; 325

Comparing DisplaysTitanic Passengers

Crew; 885

Third Class; 706

Second Class; 285

First Class; 325

Crew Third Class Second Class First Class0

100

200

300

400

500

600

700

800

900

1000

885

706

285325

Categorical Data ConditionData must be counts

or percentages of individual categories

No Overlap!Crew; 50.00%

Third Class; 32.08%

Second Class; 12.95%

First Class; 17.00%

Area PrincipleThe area

occupied by a part of the graph should correspond to the magnitude of the value it represents

Pairs of Shoes

SamErikaTiaRyanNicky

Pairs of Shoes

SamErikaTiaRyanNicky

Contingency TableIn order to look at two

categorical variables together we often arrange counts in a two-way table.

The margins of a contingency table hold the frequency distributions for the data, for each variable this is called the marginal distribution

 Right

HandedLeft Handed Totals

Males 43 9 52

Females

44 4 48

Totals 87 13 100

  Right Handed Left Handed Totals

Males 43% 9% 52%

Females 44% 4% 48%

Totals 87% 13% 100%

Conditional DistributionsIf we look at each row

separately we can see the distribution of left/right handedness under the condition of gender

These percentages are called Conditional DistributionsWhy?

  Right Handed Left Handed Totals

Males 43 9 52

  82.69% 17.31% 100%

Females 44 4 48

  91.67% 8.33% 100%

Conditional Distributions (Cont.)We can turn our

conditional distribution around and look at gender for each type of handedness.

What is the new “Who”?

  Right Handed Left Handed Totals

Males 43 9 52

  49.43% 69.23% 52%

Females 44 4 48

  50.57% 30.77% 48%

Totals 87 13 100

 100% 100% 100%

Conditional DistributionsIs your handedness

dependent on your gender?

Probably not.

These two variables appear to be independent.

Right Handed Left Handed0

5

10

15

20

25

30

35

40

45

50

MalesFemales

Segmented Bar Chart

Fin

HW: Handout