GraphingMEL 4E

Graphing data can make it easier to quickly see trends. There are different types of graphs which each show and compare data

Why do we use graphs?

Where might you see graphs?

Used to compare quantities Data is categorical Ex. monthly snowfall

Bar Graphs

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Number of students in each grade at Huron Heights

Grade

Num

ber

of

Stu

dents

What grade has the most students?What grade has the least students?How many students are in grade 11?What trend do you see for the number of students across all grades?

1. Create the axes 2. Add a scale 3. Add titles to the axes 4. Plot the bars 5. Add a descriptive title

Creating a bar graph

Create the axes

Add a scale

Horizontal axis: use categories

Vertical axis: Max is 450

9 intervals possible

450/9 = 50

So scale is 50!

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Add titles to the axes

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450

Grade

Num

ber

of

Stu

dents

Plot the bars

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450

Grade Number of Students9 20010 27511 32512 350

Add a descriptive title

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450

Number of students in each grade at Huron Heights

Used to compare 2 similar sets of data ex. Boys and girls

Double bar graphs

2006 2007 2008 2009 20100

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Number of boys and girls using the internet over time

BoysGirls

Year

Num

ber

of

Stu

dents

usin

g t

he inte

rnet

** ALWAYS Needs a Legend**

Used to compare data

Data is continuous Numbers are

grouped to form a continuous range from left to right

Ex. Allowance

Histograms

Same as the bar graph but the horizontal scale must be continuous

Range is inclusive i.e $5 fits into $5-$10 rather than $0-$5

Making a histogram

How many people scored between 0-20% ?

$5, $10, $5, $20 $0, $4.50, $10, $12$0, $20, $15, $5 $25, $5, $20, $15

Bar Graph vs. Histogram

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Allowance of students

Allowance ($)

Num

ber

of

Stu

dents

0--5 5--10 10--15 15--20 20+0

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2

3

Allowance of students

Allowance ($)

Num

ber

of

stu

dents

If 10 Students’ marks are 40 46 49 57 58 73 75 81 84 96

40 46 49 57 58 73 75 81 84 960

1

2

Bar Graph

Mark on Final Exam

Num

ber

of

Stu

dents

40-49 50-59 60-69 70-79 80-89 90-990

0.5

1

1.5

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2.5

3

3.5

Histogram

Mark on Final Exam

Num

ber

of

Stu

dents

40-49 50-59 60-69 70-79 80-89 90-990

0.5

1

1.5

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2.5

3

3.5

Histogram

Mark on Final Exam

Num

ber

of

Stu

dents

40-49

50-59

60-69

70-79

80-89

90-99

0 0.5 1 1.5 2 2.5 3 3.5

Histogram

Num

ber

of

Stu

-dents

Mark

on F

inal Exam

Useful for showing relationships (like change over time) Data is ordinal Ex. Average temperature

Line Graphs

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Grades vs. Absences

Number of Absences

Gra

de

What grade did a person with 20 absences get?

How many absences did a person who got 60% have?

What grade would you expect a student with 17 absences to get?

What can you say about the relationship between grades and absences

Same as the bar graph but...◦ Plot dots instead of bars◦ Connect points with a ruler◦ Horizontal scale must be in numerical order

Making a line graph

Absences Grade 2 90 5 75 8 80 14 60 20 40 24 32

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Grades vs. Absences

Number of Absences

Gra

de (

%)

Used to compare 2 similar sets of data that change over time

Double line graph

Number of children who are adopted and brought into foster care vs. time

Used when sections represents portions of a whole

Ex. Percent who chose pizza

Pie/Circle Graphs

What percent of people chose Apple pie?If 100 people took the survey, how many chose Pecan pie?

If 50 people took the survey, how many chose pumpkin?

How could you estimate the percent of people who chose cherry pie if the label was not included?

Each dot represents 1/100 of the circle Count out the percent of the circle for each

category Use a ruler to separate the pieces

Making a Pie Chart

A descriptive title Labels on each axes/Segment A scale Units Data Points!

Every Graph Needs