how to choose which graphic to use

WHICH GRAPHIC TO USEHow to Choose

there are three main types of graphic

bar chart pie chart line graph

all three are used to display different kinds of data

let’s have a look at some examples

using a class of 30 students

and information about their social media use

BAR CHARTS

bar charts are good for showing discrete categories

of data

let’s say we wanted to find out which social media apps

they use

so we ask them to answer a survey telling us which apps

they use

it should give us a table that looks like this

Snapchat 19

Twitter 21

Instagram 17

Facebook 12

Other 11

as the total is more than 30, we can see that most of them

use more than one app

Snapchat 19

Twitter 21

Instagram 17

Facebook 12

Other 11Total = 80

if we add all the responses together, we get more than 100%

this means the people who use each app are a discrete group

if the number of people using one app increases, it doesn’t mean the number of people using other apps goes down

Snapchat 26

Twitter 21

Instagram 17

Facebook 12

Other 11

because we want to compare how may people use each app

we need to display the information in a bar chart

0

10

20

30

Snapchat Twitter Instagram Facebook Other

PIE CHARTS

pie charts are good when we want to show parts of a whole

now, let’s say we wanted to find out which app they use

the most

so we ask them to answer another survey, telling us their

favorite app

we should get a table that looks like this

Snapchat 9

Twitter 14

Instagram 3

Facebook 2

Other 2

this time, because each person only selected one app, we have a closed group of 30 responses

so when we add the different subgroups together, we get 100%

this means we can consider each subgroup a percentage of

the whole class

so we need to display the information in a pie chart

7%7%

10%

30%

47%

TwitterSnapchatInstagramFacebookOther

LINE GRAPHS

line graphs are used to show how things change

usually over time

the surveys we’ve done so far don’t show us any kind of change

but let’s say we wanted to see how the results changed

we could do one of the same surveys repeatedly

so let’s say we ask them to answer the survey about their

favorite app

and we ask them at the beginning of every year

we’d get a table that looks like this

2014 2015 2016 2017

Snapchat 2 3 3 9

Twitter 10 14 19 16

Instagram 4 5 3 3

Facebook 14 8 5 2

now we can see that people’s favorite app has changed over time

and we can show this with line graph

0

5

10

15

20

2015 2016 2017 July

Snapchat Twitter Instagram Facebook

so all three kinds of chart show different kinds of data

bar chart pie chart line graph

discrete groups

parts within a whole

change over time

now you know which one to use

END