Week 4

LSP 120

Joanna Deszcz

3 Types of Graphs used in QR Pie Charts

Very limited useCategory sets must make a whole

XY Graphs or Line GraphsUse with “a lot” of data points

Bar Charts or Column ChartsVery flexibleWork well with limited data Compares more than one series

Pie Charts Only used when have

a quantitative variable associated with a list of categories

Both the categories and the quantities each add up to a whole

Categories must be disjoint – no overlapping

Most Common Pie Chart Mistakes Use on set of categories that don’t make

a whole Use on categories that overlap Include total in chart data

Let’s try an exampleLeading Causes Of Death Tab

Creating a Pie Chart Select labels and

values Choose Pie chart type Choose layout

Must include % value, title and labels

Layout 6 does it all

Add the source in a text box

Labeling the Chart Title should be descriptive

Consider who, what, when and where Percents should be formatted to 2

decimal placesFormat – Data Labels – Numbers –

Percentage – 2 decimal places Source – add in text box

Insert – Text Box – Draw text box on the chart and type in source

If not source give type “Unknown”

Chart Themes

Found on Page Layout Tab Slide mouse over built-in themes

Chart will change to reflect each theme

The Result…

Flow Theme applied to the chart

XY Graphs Used with a lot of

data X-axis categories

are numeric, (often years)

Choose xy graph option with connected data points

Note: Don’t use the Line Graph Excel line graphs always treat the x-axis

categorically instead of numerically

Causes endless array of mistakes

Use XY (Scatter) graph instead to avoid errors

Let’s try one Lake Michigan Levels Tab

Creating XY (Line) Graphs Select category

labels and values Choose Scatter

chart optionScatter with straight

lines and markers type

2nd row, 2nd column

Choose design layout 1 from Design tab

Labeling the Chart

Title should be descriptiveConsider who, what, when and where

Remove the legend from the chartNot needed when there is only one series

Source – add in text boxInsert – Text Box – Draw text box on the

chart and type in sourceIf not source give type “Unknown”

Apply a theme if you wish

Make Your Chart More Readable XY Graphs often only

take up a small range of values

If all data points located in a central area on the graphAdjust y-axis so

values start at or just below the lowest data point value

•Right-click on y-axis•Choose Format axis•Adjust Minimum value

The Result…

Solstice Theme applied to this chart

What’s the Story? XY (Line) Graphs usually tell a story about the data

Analysis should carefully describe what the graph is saying

Start the “story” from the left and move to the right

Be sure to include the high point and the low point as well as anything that is interesting or unexpected

Write a well-written paragraph telling the “story”

Describing your graph In a paragraph, point out what you want the

reader to know about the graph Examples:

“In the Annual Averages of Lake Michigan/Lake Huron Water Levels chart we find that between 1988 and 1997 water levels in the lakes increased overall. The high point of the lake levels occurred in 1997 when the level was 176.98 meters. However, lake levels took a sharp decline in the following 2 years and reached their low point in 2003 when the level was only 175.89 meters. Since 2003 lake levels have increased slightly but appear to be declining once again.”

Bar Chart or Column Chart Very flexible Used when a

quantitative variable is associated with the a categorical variable

Work well with limited data

Can compare more than one series

Note: Be Careful

If you do use a bar chart and have years along the x-axis

Be sure the years are in equal intervals.  Otherwise, you can be guilty of creating

a misleading graph

Let’s try one Home Heating Tab

Creating a Column Chart Select the data

including category labels and values

Choose Column Chart2-D Clustered column

option

Add Titles and axis labelsLayout 9 works well

Labeling the Chart

Title should be descriptiveConsider who, what, when and where

Both the x-axis and y-axis should be labeled

Source – add in text boxInsert – Text Box – Draw text box on the

chart and type in sourceIf not source give type “Unknown”

Apply a theme if you wish

Name Each Series in the legend To change names

Click on chart to activate

Click on Design TabUnder Data Group –

choose Select DataData Series labels

appear on leftHighlight label and

click edit button Type new series

name in Edit Series Dialog box

The Result…

Aspect Theme applied to chart

Source: US Dept of Energy

Add the other column of data Reselect the data to include all 3

columns

The New Result

Source: US Dept. of Energy

Advantages of Multiple Bar Charts Succinctness Can make comparisons within

categories and across categories Best used in printed works

Can be carefully studied

Disadvantages

Can present too much information to view as part of presentation

Hard to make a single clear point with bar charts

Presenters don’t leave them up long enough to absorb info fully

Describing a Bar/Column Chart Usually include high and low values in

graph description Not always effective/appropriate with

bar/column charts Include top 2 or 3 values instead Low value may be insignificant

Often describes “Other” categoryNot significant in the “story”

Guidelines for Creating an Effective Graph1. What is the purpose of making a graph

from this data?

2. What type of graph should you make?  Pie, bar, x-y scatter (line)   

3. Decide on a title and consider the W's (who, what, where and when)

4. Do you need to include a legend? 

Guideline continued…

5. Add a descriptive x-axis and y-axis label for bar and xy-scatter graphs

6. Add percentages for pie charts, 2 decimal places

7. Adjust the scale for bar and xy-scatter graphs (if applicable)

8. Add source

Can the Graph Stand Alone? A good graph should be able to stand

alone Without any words to tell the reader what

they are looking at

If the reader doesn't understand the graph without a caption (or story) then the graph isn't very good

Faulty or Misleading Graphs Data can be displayed "correctly" yet

gives different messages depending on how it is displayed

Y-axis Scale Effects

Most common way to create a misleading graph

Y-axis scale should begin at 0 Not always the case Can work in favor of the one distributing

the graph

Bad Chart Examples

What’s wrong with this chart

Another Bad Example – Misleading Graph

Graph appeared in Chicago Tribune and on billboards along the Kennedy Expressway