Had a look
Nearly there
PROBABILITY
& STATISTICS
Nailed it!
Line graphs
A time series graph is a line graph that shows how a variable changes over a period of
time. This time series graph shows median incomes in the UK from 1980 to 2010.
The graph should have a title.
The graph shows an upward
trend. This means that in general,
as time passes, the median
income increases.
The vertical axis shows the
variable which changes over time.
Median income
(£1000s)
UK median incomes
30
25
20
15
10
5
0
1980 1990 2000 2010
Year
The horizontal axis always shows
units of time.
Vertical line graphs
A vertical line graph is sometimes
called a bar-line graph. It works in
the same way as a bar chart but
the bars are straight, vertical lines.
This vertical line graph shows the number of pairs
of trainers owned by the members of a class.
Frequency
You can revise bar charts on page 117.
!
This is like finding the mean from this
frequency table:
Number of pairs of 0 1 2 3 4 5 6
trainers
Frequency
0 4 7 6 2 0 1
Work out the total number of pairs of trainers
owned, then divide by the total number of
members of the class.
You can revise how to find the mean from a
frequency table on page 121.
You will need to use problem-solving skills
throughout your exam – be prepared!
The table on the right gives
information about the percentage of
students who passed a professional
exam each year from 2007 to 2013.
(a) Draw a time series graph to
represent this data. (3 marks)
(b) Describe the trend. (1 mark)
8
7
6
5
4
3
2
1
0
0
1
2
3
4
5
Number of pairs of trainers
6
What was the mean number of pairs of trainers
owned?
(2 marks)
Total number of pairs of trainers owned
0×0+4×1+7×2+6×3+
2 × 4 + 0 × 5 + 1 × 6 = 50
Total number of members of class
0 + 4 + 7 + 6 + 2 + 0 + 1 = 20
50 ÷ 20 = 2.5
The mean is 2.5 pairs of trainers.
Year
2007 2008 2009 2010 2011 2012 2013
Percentage (%) 58
60
53
55
63
65
73
You can use a ‘break’ in
your vertical axis.
55
50
123