1.2 Representing data


In Linking Thinking 1 we learned how to represent data using frequency tables, line plots, bar charts and histograms. We will now look at representing data in pie charts and stem and leaf plots.


Pie charts


A pie chart is a circular (360°) graph which shows the proportion that different categories contribute to an overall total.


In the pie chart shown you can clearly see that the preferred type of movie of the people questioned was romance, because it has the largest sector. Drama was the least favourite type of movie because it has the smallest sector.


Worked example 1 The pie chart shows the preferred breakfast choices of a group of teenagers.


(i) What percentage of the teenagers preferred pancakes? Justify your answer.


(ii) What is the measure of the angle representing the number of teenagers that preferred toast?


(iii) If 180 teenagers preferred eggs, how many teenagers in total were questioned?


(iv) If a teenager was picked at random from the entire group, what is the probability that they preferred cereal?


Solution (i)


(iii) Cereal 110° 72° Eggs Toast Pancakes


By the end of this section you should be able to: ● draw and interpret pie charts ● draw and interpret stem and leaf plots


● decide the most appropriate graph to represent the data


Favourite type of movie Sci-fi


Comedy Drama Romance Action


(ii)


(iv)


Drawing a pie chart Find the total number surveyed.


1 3 5


Work out the angle for each category by multiplying each fraction by 360°.


Remember: the angle in a full circle is 360°.


2 4


Represent each category as a fraction of the total.


Marking a centre, use a compass to draw a circle. Using a ruler, draw a start line from the centre to a point on the circle.


Use a protractor placed on the start line to begin measuring each of the angles around the circle. Each line drawn becomes the start line for the next angle.


Section A Applying our skills 5


1


Statistics 1


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