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Building number confidence: Graphical data

4. Charts and graphs

4.1. Pie chart

A pie chart is a circular chart, cut into segments, or slices. Each segment represents a proportion of the whole and can quickly demonstrate where there are wide differences between values.

For example, in the pie chart below, we can instantly see that Americanos accounted for nearly half of all sales on Monday.

A pie chart showing cafe sales with largest segment for Americanos.

Data from: .

  Americano Latte Flat white Cappuccino Tea
Monday 76 14 20 12 35
Tuesday 60 30 14 25 17
Wednesday 57 28 30 22 25
Thursday 37 32 12 27 14
Friday 70 36 18 32 28
Saturday 72 35 27 16 32
Sunday 55 25 23 27 40

Although the visual impact of the different sized segments is perhaps the main reason you might choose a pie chart, data labels can also be included. In this example the data labels provide actual quantities sold for each category.

A pie chart with data labels added showing that American sales on Monday totaled 76

 

A pie chart provides visual impact for a snapshop of data. Another chart type would be more appropriate where access to multiple sets of data is required. For example, a pie chart could not show the breakdown of tea and coffee sales, for each day of the week, as we could do with a bar chart.

 Data check

This chart shows the total numbers of each category sold during one week, with Americano being the clear favourite. Which category had the smallest number of sales?

Pie chart with 5 segments representing sales of Americano: 427, Latte: 200, Flat white: 144, Capuccino 161, Tea: 191

Flat whites were the least requested drink during this week: the number sold was 144.

 

 Data check

This pie chart shows the different travel to work methods used by staff working for a local business.

A pie chart with staff travel data: Bus (19), Car (27), Walk (12), Bicycle (11), Motorcycle (4).

Data from: .

Bus Car Walk Bicycle Motorcycle
19 27 12 11 4
  1. What is the method of travel used by most staff?
  2. How many staff walk to work?
  3. How many staff in total were surveyed?

  1. Most of the staff (27) use a car to get to work.
  2. Twelve (12) members of staff walk to work.
  3. The total number of staff surveyed was 73. This is the sum of all the segment data labels.