# Bar Charts and Line Graphs

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Bar Charts and Line Graphs
Teach GCSE Maths 40 Number of Parking Tickets 10 20 30 Monday Tuesday Wednesday Thursday Friday Pictograms Friday Thursday Wednesday Tuesday Monday Bar Charts and Line Graphs

Pictograms, Bar Charts and Line Graphs
Data from the Office for National Statistics which is included in this presentation is reproduced under the terms of the click-use licence. "Certain images and/or photos on this presentation are the copyrighted property of JupiterImages and are being used with permission under license. These images and/or photos may not be copied or downloaded without permission from JupiterImages" © Christine Crisp

20 5 35 40 Diagrams are often used to show information from data.
e.g. The following data set shows the number of cars given parking tickets on a particular street on 5 weekdays. Monday Tuesday Wednesday Thursday Friday 20 5 35 40 As always, the frequencies are numbers, but we don’t have numbers for the days of the week. The data are qualitative (descriptions ) instead of quantitative (quantities or numbers ). Both types of data can be shown in pictograms and bar charts.

20 5 35 40 20 Number of Parking Tickets e.g. A pictogram of the data.
Monday Tuesday Wednesday Thursday Friday 20 5 35 40 20 e.g. A pictogram of the data. Number of Parking Tickets pictogram  picture Friday Thursday Wednesday Tuesday Monday Decide with your partner how many real cars are represented by a picture of a car. Key: = 10 cars The diagram must have a title and key. Ans: 10

There is very little difference between a pictogram and a bar chart.
We replace the pictures with bars ! Number of Parking Tickets Friday Thursday Wednesday Tuesday Monday 10 20 30 40 As before, we must have a title but instead of a key we have a scale. Bar charts are easier to draw using squared paper.

Bar charts are often drawn with the bars going up the page.
40 Number of Parking Tickets 10 20 30 Monday Tuesday Wednesday Thursday Friday 40 Number of Parking Tickets 10 20 30 Friday Thursday Wednesday Tuesday Monday Friday Thursday Wednesday Tuesday Monday Number of Parking Tickets 10 20 30 40 Friday Thursday Wednesday Tuesday Monday Number of Parking Tickets 10 20 30 40 Friday Thursday Wednesday Tuesday Monday Number of Parking Tickets 10 20 30 40 To find the mean number of tickets issued per day, we sum the frequencies and divide by the number of days.

Bar charts are often drawn with the bars going up the page.
Number of Parking Tickets Friday Thursday Wednesday Tuesday Monday Number of Parking Tickets 10 20 30 40 Friday Thursday Wednesday Tuesday Monday Number of Parking Tickets 10 20 30 40 40 30 20 10 mean number of tickets issued per day Friday Monday Tuesday Thursday Wednesday 20 + 20 + 5 + 35 + 40 = = 24 5

Methods of Transport to School
Double, or dual, bar charts can be used to compare data. This chart compares the way that boys and girls in a junior class travelled to school. Frequency 2 4 6 8 10 12 Bus Train Taxi Walking Methods of Transport to School Boys Girls With your partner answer the following: (a) How many girls go by train? (b) How many children go by taxi? (c) What is the most popular way of getting to school? Ans: (a) 2 (b) 4 (c) Walking

A line graph is mostly used when data are given at regular intervals of time. For example, times of day, months, or years. Year Number (millions) 1991 15.1 1993 18.4 1995 19.2 1997 16.5 1999 14.8 2001 12.6 e.g. The table shows the total number of recorded crimes in England and Wales. Draw a line graph to display the data. Solution: We plot the years on the x-axis (horizontally) and the number of crimes up the y-axis (vertically). The points are joined with straight line segments. Source: Office for National Statistics: British Crime Survey, Home Office

Total Number of Crimes committed in England and Wales
Solution: Total Number of Crimes committed in England and Wales Year Number (millions) 1991 15.1 1993 18.4 1995 19.2 1997 16.5 1999 14.8 2001 12.6 x x x x x x Number (millions) 1991 1993 1995 1997 1999 2001 Year Between 1991 and 2001, most crimes occurred in 1995. Crime decreased each year from 1995 to 2001. ( Other answers are possible. ) Tell your partner 2 things the graph tells you about the number of crimes.

Exercise 1. The diagram shows the spending by overseas tourists in parts of the U.K. in 2001. SW England Heart of England Wales Scotland Area Source: Office for National Statistics Key: = £100 million (a) How much was spent by the tourists in (i) the Heart of England and (ii) Wales? (b) The figure for SW England was £ How many pictures would show this?

(i) £700 million was spent in the Heart of England
Exercise Answers: Area Scotland Wales Heart of England SW England Source: Office for National Statistics Key: = £100 million (i) £700 million was spent in the Heart of England (ii) £250 million was spent in Wales. (b) 4½ pictures are needed to show £

2. The diagram shows the estimates of fish stock in the North Sea in the 1970s and 1990s.
North Sea Fish Stocks 1000 2000 3000 Cod Herring Haddock Frequency ( thousands of tonnes ) 70's 90's Source: Office for National Statistics (a) Which type of fish stock increased between the 1970s and the 1990s? Ans: Herring (b) What was the estimate of the stock of cod in the 1970s? Ans: ( 800 thousand ) tonnes

SUMMARY Qualitative data has descriptions instead of numbers. e.g. days of the week, colours, transport methods. Pictograms and bar charts can be used to display qualitative and quantitative data. Pictograms must have a title and a key. The key gives the frequency for each picture. The lengths of the bars on a bar chart give the frequencies. Bar charts must have a title and a scale. Line graphs have straight line segments joining the points. The x-axis often shows time.