Cambridge International Mathematics

114 Graphs, charts and tables (Chapter 5)

STEM-AND-LEAF PLOTS

Astem-and-leaf plot(often called a stem-plot) is a way of writing down the data in groups and is used for

small data sets. It shows actual data values and gives a visual comparison of frequencies.

For numbers with two digits, the first digit forms part of thestemand the second digit forms aleaf.

For example, for the data value 17 , 1 would be recorded on the stem, and the 7 would be the leaf value.

Example 4 Self Tutor

Construct a stem-and-leaf plot for the following data:

25 38 17 33 24 16 32 17 22 35 30 44 20 39 42 37 26 31 28 33

Thestem-and-leaf plotis:

Stem Leaf

1 767

2 542068

3 832509713

4 42

Theordered stem-and-leaf plotis:

Stem Leaf

1 677

2 024568

3 012335789

4 24 Key: 1 j 7 means 17

The ordered stem-plot arranges all data from smallest to largest.

Notice the following features:

² All the actual data is shown

² The minimum (smallest) data value is 16 :

² The maximum (largest) data value is 44 :

² The ‘thirties’ interval ( 30 to 39 ) occurred most often, and is themodal class.

² The key indicates the place value of the stem. For example, if the key was 1 j 7 means 1 : 7 then

2 j 3 would represent the data value 2 : 3.

EXERCISE 5A

1 Of the 30 teachers in a school, 6 teach Maths, 7 teach English, 4 teach Science, 5 teach Humanities

subjects, 4 teach Modern languages, 2 teach Theatre Arts, and 2 teach Physical education.

a Draw a vertical bar chart to display this information.

b What percentage of the teachers teach Maths or Science?

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Y:\HAESE\IGCSE01\IG01_05\114IGCSE01_05.CDR Monday, 15 September 2008 12:52:04 PM PETER