6/13/2015BUS304 – Data Presentation1 Graphs Visual presentation of data Pie Chart Bar Chart Line Chart Scatter Chart

04/18/23 BUS304 – Data Presentation 1

Graphs

Visual presentation of data

Pie Chart

Bar Chart

Line Chart

Scatter Chart


A good graph should

Accurately conveys the information

Grabs the reader’s attention (visually enjoyable)

Complements or demonstrates arguments presented in the text

Is simple and uncluttered

Clearly shows trends or differences in the data

Is visually accurate (i.e. one chart value is 15 and another is 30,

then 30 should be twice the size of 15)


Average Gas Prices from 1999-2002

$0.00

$0.20

$0.40

$0.60

$0.80

$1.00

$1.20

$1.40

$1.60

1999 2000 2001 2002

Year

Pric

e P

er G

allo

n

Average Unleaded Price

Average Premium Price


No. of People that have each investment

Mutual Fund22%

Savings Account

31%Certificate of

Deposit9%

Individual Stocks21%

Bonds5%

Real Estate10%

Other2%


Why use graphs?

Graphs

Are quick and direct

Highlight the most important facts

Facilitate understanding of the data

Can convince readers

Can be easily remembered.Most of the time, creating graphs is more of an art. Both visually correct data can create different

Most of the time, creating graphs is more of an art. Both visually correct data can create different


Not always good to use graphs

The data are very dispersed The data are very numerous


Not always good to use graphs

There are too few data The data show little variations

Sometimes, you may need to try different graphs, and may determine not to use graph in the end.

Sometimes, you may need to try different graphs, and may determine not to use graph in the end.


Bar Charts Horizontal bars or vertical bars (also called “columns” in Excel)

Used to represent categorical data Each bar (column) represents one category

The width (height) of the bar represents the number in the category

Horizontal bar chart provides more space for category names

Vertical bar shows a clearer trend when representing yearly data

0 10 20 30 40 50 60

1993

1994

1995

1996

1997

1998

0

10

20

30

40

50

60

1993 1994 1995 1996 1997 1998


Create a basic bar chart Open file “data2.xls” Create two bar charts using the data in Data Sheets

“Column Chart” and “Bar Chart”


Other Bar Charts

Side by side bars / stacked bars / 100% stacked bars when more than one piece of info in one category

Create these three charts using data from worksheet Side-by-side. Write down, for each chart, the primary information the chart conveys.

Legend is important in those charts

Legend is important in those charts


March 2005 New Car Sales

Car Company March 2005 Sales

General Motors 426,114

Ford 305,173

DaimlerChrysler 243,165

Toyota 203,443

Honda 128,548

Nissan 106,042

Chg from Mar 2004

-1.1%

-5.4%

+2.7%

+12.2%

+6.9%

+12.5%

Create a bar chart to represent the sales of Mar 2005 for different brands.Then discuss with another student (group of 2) to create a new graph characterizing the information on the 3rd column. (You can draw the graph,if you are not sure how excel can convey the information.


Pie Chart A way of summarizing a set of categorical data Convenient to present the proportion of each category It is generally more difficult to convey the actual amount

Works especially when there are not too many categories and the proportions are significantly different from categories.

Percentage of People Investing

Mutual Fund22%

Savings Account

31%Certificate of Deposit

9%

Individual Stocks21%

Bonds5%

Real Estate10%

Other2%

Mutual Fund

Savings Account

Certificate of Deposit

Individual Stocks

Bonds

Real Estate

Other


ExerciseUse the data in “Bar Chart” to create a bar

chart. Compare it with the bar chart. Discuss the different information it conveys


Mis-use of a pie chart A pie chart focuses the readers attention on the “proportion”.

Unlike bars, which can be created with multiple series (side-by-side bars), pie chart is focused on one series.

Wrong:

why? 430853.3873

322593.0233

236772.1519

181321.7469

120250.7016

94259.55556

426,114

305,173

243,165

203,443

128,548

106,042General Motors (03/04)

Ford (03/04)

DaimlerChrysler (03/04)

Toyota (03/04)

Honda (03/04)

Nissan (03/04)

General Motors (03/05)

Ford (03/05)

DaimlerChrysler (03/05)

Toyota (03/05)

Honda (03/05)

Nissan (03/05)


Discuss: Student leaders at Boise State University wanted to draw attention to the

funding inequities among the four public universities in Idaho. They collect the following information:

Funding Per Student

Boise State Univ. Univ of Idaho Lewis & Clark College Idaho State Univ.

$5,900 $7,143 $6,320 $5,410

The student leader created

a par chart as shown on the

right to represent the data he

collected. Please comment on

his chart.


Line Chart

Especially useful in statistics and science. To reflect the trend.

Can draw multiple lines in one graph for comparison.

0

200

400

600

800

1000

1200

1400

1600

1800

2000

1996 1997 1998 1999 2000 2001 2002

No. of Men

No. of Women

Note: when using Excel to generate a line chart, the X-axis is stillregarded as categorical names.It does not have numerical value

Note: when using Excel to generate a line chart, the X-axis is stillregarded as categorical names.It does not have numerical value

Exercise: Sheet 4 and 5

Line Chart with Secondary Axis Go to Line Chart 3. The data contains both the Sales and Profit

over the years. Create two line chart, one for sales data, one for profit data. Question: how do we combine these two lines in one chart?



Scatter Chart Mostly used in science and statistics to reflect the

sample location. X-axis and y-axis both have numerical values Shows data correlations (positive, negative, etc.)


Observe data correlation from scatter chart

Find the data from worksheet 6.

Draw scatter chart using

Sq. Feet as x-axis, Price as y-axis

Age as x-axis, Price as y-axis

No. of bedrooms as x-axis, Price as y-axis

No. of bathrooms as x-axis, Price as y-axis

No. of garages as x-axis, Price as y-axis


Summary

4 Basic types of charts:

Bar chart

Pie chart

Line chart

Scatter chart

Know how to create a

chart from Excel

Know how to read the

chart (find a value given

a certain condition)

Know the characteristics,

and be able to pick the

best chart to convey info.

Grouped Data

04/18/23 BUS304 – Data Presentation 23BUS304 – Data Presentation 23

From Raw Data …Raw Survey Data

Raw Survey Data

Surveyee Favorite Cuisine

#1 A

#2 D

#3 E

#4 C

#5 B

#6 E

#7 A

#8 E

#9 C

#10 D

#11 D

… …

What is your favorite type of cuisine?

A) Chinese

B) French

C) Indian

D) Italian

E) Other

04/18/23 BUS304 – Data Presentation 24BUS304 – Data Presentation 24

Frequency Table

Tells us information on the aggregate level

i.e. How many data fall in one specific category

Such information is most statisticians care about

Can be used to transfer to graphs

Frequenc

y

Chinese 10

French 4

Indian 3

Italian 8

Other 4

Total 29

Favorite Cuisine Types

0

2

4

6

8

10

12

Chinese French Indian Italian Other

04/18/23 BUS304 – Data Presentation 25Feb 1, 2006 BUS304 – Data Presentation 25

Relative FrequencyRelative Frequency:

The percentage of times

FrequencyRelative Frequency =

Total Sample of Population Size

Frequency

Chinese 10

French 4

Indian 3

Italian 8

Other 4

Total 29

Relative

Frequency

Chinese 0.344828

French 0.137931

Indian 0.103448

Italian 0.275862

Other 0.137931

Total 1.000000

You can use either a bar chart or a piechart to represent a relative frequency table.


ExerciseCreate frequency and relative frequency tables

for both the male and female surveyees. Compare their different preferences.


For Interval / Ratio Data 16 business executives responded to the question on

how many international trips they made in 2006.

3 0 0 1

1 2 2 0

0 2 1 0

2 1 4 2

Create a frequency and relative frequency to characterize the responses.


When data spread to a wide range

Raw Data

Raw Data

Grouped Data

Grouped Data

Total

0~$10000

$10000~$20000

$20000~$30000

$30000~$40000

… …

Total

Frequency Table

Frequency TableSurveyee Gender Annual Income

#01 F 90213

#02 F 35236

#03 M 45660

#04 M 61508

#05 M 24158

#06 M 57545

#07 F 61559

#08 F 57573

… … …

We divide the data into ranges and count how many fall into the range

We divide the data into ranges and count how many fall into the range

Finish the table and create a bar chart to display the grouped dataHint: you may need to sort the raw data in ascending (or descending) order

Finish the table and create a bar chart to display the grouped dataHint: you may need to sort the raw data in ascending (or descending) order


Histogram

0

3

6

5

4

2

00

1

2

3

4

5

6

7

5 15 25 36 45 55 MoreF

req

uen

cy 0~9 10~19 20~29 30~39 40~49 50~59 More

Histogram

Also called “frequency histogram”

A bar chart converted from the

frequency table:

displays the data distribution:

X-axis shows the data range

Y-axis shows the number of data

fall in to the group

Generally don’t have gap between

bars – why?

Histogram is only for displaying

“continuous interval/ratio data”

Exercise:Adjust the bar chart you havefrom last page to a histogram

Exercise:Adjust the bar chart you havefrom last page to a histogram


Steps to create a histogram

1. Figure out how to group the data

Find the minimal data (rounded down)

Find the maximal data (rounded up)

Find the rough range = max – min

What does the range mean?

Determine how many groups you want to display?

(Not too many, but not too few)

Define the Interval (How wide is each group)

Interval = (range of Data) / (no. of groups)

Generate the ranges and create frequency table

Convert the frequency table to a bar chart (with no gap!)


Extra Notes The actual shape of the histogram depends on the

number of groups Exercise: try to create a histogram using the income data

(data3, sheet2) with 6 groups, 10 groups and 15 groups. Read:

• How many people have an annual income higher than $60000?

• How many are lower than $30000?

Think: • What if I only have 2 groups?

• What if I have 30 groups?

Histogram

0

20

40

60

80

10000~54999 55000~99999 More

Fre

qu

en

cyFinding the right number of

groups to best present the data distributionmay take you several trials.

Finding the right number of groups to best present the data distributionmay take you several trials.

Documents

6/13/2015BUS304 – Data Presentation1 Graphs Visual presentation of data Pie Chart Bar Chart Line Chart Scatter Chart