Cambridge International Mathematics

Graphs, charts and tables (Chapter 5) 117

Compound bar chart of screw cap data Back-to-back bar chart of screw cap data

We can see from the graphs that machine B generally produces more faulty screw caps than machine A.

Example 5 Self Tutor

15 students were examined in Geography and Mathematics. The results were:

Geography 65 70 56 67 49 82 79 88 47 76 69 58 90 45 82

Mathematics 75 67 81 88 84 66 77 72 60 58 67 71 74 82 89

Use an ordered back-to-back stem-and-leaf plot to compare the results.

Before ordering:

Geography Mathematics

579 4

86 5 8

975 6 7607

690 7 57214

282 8 18429

0 9 Key: 8 j 2 means 82

After ordering:

Geography Mathematics

975 4

86 5 8

975 6 0677

960 7 12457

822 8 12489

0 9 Key: 8 j 2 means 82

From the plot we observe that:

² the Geography marks are more spread than those for Mathematics

² the Mathematics marks are generally higher than those for Geography.

EXERCISE 5B

1 In each of the following graphs, two data sets of the same size are compared. What can be deduced

from each graph?

ab

0

5

10

15

20

25

30

2345678910111213

Machine A

Machine B

30 20 10 0 10 20 30

2

4

6

8

10

12

Machine A

Machine B

is A

is B

BA

We can compare the data for the two machines using a compound bar chart or back-to-back bar chart:

IGCSE01

cyan magenta yellow black

(^05255075950525507595)
100 100
(^05255075950525507595)
100 100
Y:\HAESE\IGCSE01\IG01_05\117IGCSE01_05.CDR Thursday, 18 September 2008 11:55:54 AM PETER