Secondary National StrategyHandling Data

Graphs and charts

Created by J Lageu, KS3 ICT Consultant – Coventry

Based on the Framework for teaching mathematics pages 248 - 275

KS3 Handling Data

Graphs & charts a handy guide

Click on the required choice

Types of data

Types of graph or chart

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KS3 Handling Data

Data types

Categorical

Discrete

Continuous

Grouped discrete

Grouped continuous

Means

KS3 Handling Data

Categorical

data is broken into categories, there is no order to the categories eg

– gender - male, female

– transport method – walk, bus, train etc

possible graph & chart choices

– pie chart

– bar chart

– compound bar chart

– bar line graph

– pictogram

KS3 Handling Data

Discrete

data is numerical with separate values

– counted eg no of letters in a word, no on a dice

– ordered but not counted eg school year group, size of shoe

possible graph & chart choices

– pie chart

– bar chart

– compound bar chart

– bar line graph

– pictogram

KS3 Handling Data

Continuous

data is numerical and is measured

– length, weight, time etc.

– even if there is rounding, say to the nearest hour, it is still continuous. We are approximating, but there is still meaning to in between points.

– digital clock is continuous because it approximates.

– exception - shoe size is discrete because it is labelling a type of shoe. There are only ever a certain number of shoe sizes and there is no shoe size between 3 & 3½.

possible graph & chart choices

– frequency diagram

– frequency polygon

– line graph

– scatter graph

– cumulative frequency diagram

KS3 Handling Data

Grouped discrete

discrete data grouped into suitable class intervals

– intervals should be equal

– there should be no overlap eg 0-5, 5-10 etc is wrong, where does 5 go?

– unequal intervals makes the data categorical eg ages: 0-5, 6-10, 11-16, 17-21, over 21

possible graph & chart choices

– bar chart

– compound bar chart

KS3 Handling Data

Grouped continuous

continuous data grouped into suitable class intervals

– intervals usually equal

– there should be no overlap eg 0 < t < 5, 5 <= t < 10

– un-equal intervals need histograms, post KS3

possible graph & chart choices

– frequency diagram

– frequency polygon

– line graph

– cumulative frequency diagram

KS3 Handling Data

Mean

mean calculated for continuous data normally over a period of time eg monthly average

possible graph & chart choices

– line graph

KS3 Handling Data

Types of graph and chart

Pie chart

Bar chart

Compound bar chart

Bar-line graph

Pictogram

Frequency diagram

Frequency polygon

Line graphs

Scatter graph

Cumulative frequency diagram

KS3 Handling Data

Pie chart

3D distorted are not strictly correct, because the angle should be proportional to the frequency

Walk Car Other Train Minibus Taxi Public bus School bus Bicycle28% 39% 1% 2% 1% 1% 10% 15% 3%

Journeys to and from school: Year 7 pupils

Walk

Car

Other

Train

Minibus

Taxi

Public bus

School bus

Bicycle

Are you using the power of technology?

I 'm on the

I nternet

I 'm not!

avoid unless you have a

specific purpose

KS3 Handling Data

Bar chart

Notice the gaps between the bars

Labels in the middle of the bars

0

10

20

30

40

50

60

70

Walk Bicycle Car/van Privatebus

Localbus

Rail Other

Form of travel

Per

cent

age

of p

upils

1985-19861998-2000

Main form of travel to school: pupils aged 5 to 10

two bars per category

grouped data

legend

KS3 Handling Data

Compound bar chart

Notice the gaps between the bars

key

labels on bars

KS3 Handling Data

Bar-line graph

The length of the bar represents the frequency.

What is being counted or measured (the independent variable) is placed on the horizontal axis, and the count or measure (the dependent variable) on the vertical axis.

It is not appropriate to join the tops of the bars.

KS3 Handling Data

Pictogram

all symbols should be the same size & shape

fitness for purpose may justify differences, but size must be the same

scale

half picture=1

identical pictures

mathematically incorrect

KS3 Handling Data

Frequency diagram

Notice there are no gaps between the bars

indicating non-zero

start

labels start & end of bars

see frequencypolygon

KS3 Handling Data

Frequency polygon

Points are plotted at the middle of the range if grouped

see frequencydiagram

KS3 Handling Data

Line graph

data point middle month & year labels

KS3 Handling Data

Scatter graph – two variables

line of best fit

KS3 Handling Data

Cumulative frequency diagram

median