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© Peter Broadfoot 2008
Histograms
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Summary of AQA Examiners Report on the Maths Module 1 Intermediate, March
2005, Question 7
The report mentions that a few candidates got the axes the ‘wrong way round’. Most correctly
used a linear y-axis with the scale divisions equally spaced, but most did not use a continuous x-
axis. Many plotted the heights correctly and most made only a single error. Two common errors
with frequency polygons: didn’t join the points; didn’t plot the mid-points.
Grid for the Sample Exam Question
Note about Class Boundaries
In an exam question you may see a slight variation on the definition of a class interval. In
the sample exam question (previous page) one of the intervals is shown as 150 ≤ x < 200. It
means that, for continuous data, values from 150 up to but not including 200 are in the
class.
An alternative is to group as in 150 < x ≤ 200. It means that 200 is included but 150 is not.
Either of these alternatives could be used in a question. It makes no difference to the way
you draw the graph of continuous data. In both cases the lower and upper class boundaries
are 150 and 200, and the mid-point is 175. You label the axes in the same way. Most of the
relevant questions in the exam are about continuous data – so there should be no problem.
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