Pie Charts

Why a Pie Chart? Very visual Easy to read Slices show clearly how the data is distributed

Data for a Pie Chart Favourite Drink Frequency Milk 7 Orange 9 Cola 13 Water 6 Tea 2 Other 3 Usually given in a table format This data was obtained from a class survey on “Favourite Drinks” How many people said they preferred this drink These are the answers given Other allows for “unexpected” answers

1 Work out the slices Favourite Drink Frequency Milk 7 Orange 9 Cola 13 Water 6 Tea 2 Other 3 We need to calculate the size of each slice in the pie chart 40 people responded to the survey If very person had their own slice, each would get the same X 360º of the circle = 9º Total 40

If 1 person is 9º Favourite Drink Frequency Milk 7 Orange 9 Cola 13 Water 6 Tea 2 Other 3 Angle 7 x 9 = 63º 9 x 9 = 81º 13 x 9 = 117º 6 x 9 = 54º 2 x 9 = 18º 3 x 9 = 27º Total 360º

2 Draw the Pie Chart Use compasses x x Use compasses Draw a circle with centre on the mark Mark a centre for the Pie Chart Or draw around an Angle Measure

2 Draw the Pie Chart Draw line vertically from centre to circumference Draw LARGEST slice first i.e. Cola = 117º Cola x Label the slice ‘Cola’ Do not enter the angle or the frequency!

2 Draw the Pie Chart Draw NEXT LARGEST slice i.e. Orange = 81º Turn Protractor so that 0º marker is at the end of line just drawn Cola Orange

2 Draw the Pie Chart Then Milk = 63º Cola Milk Orange

2 Draw the Pie Chart Then Water = 54º Water Cola Milk Orange

2 Draw the Pie Chart Then Other = 27º Other Water Cola Milk Orange

2 Draw the Pie Chart The LAST slice is already drawn – just check it Tea = 18º Tea Other Water Give the Pie Chart its Title Cola Milk Orange Class 7A’s Favourite Drink Remove the small guide marks carefully