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AS Statistics Revision
Statistics 1 Chapter 2
Representation of sample data
Key points to remember
Data = a series of observations, measurements or facts.
Variable = that which is measured or observed, e.g. height.
Type of Variable
Quantitative variable = one with measurements as numbers.
Qualitative variable = one to which numbers cannot be
Discrete variable = one taking any value within a given range.
Continuous variable = one taking any value within a given
Frequency distribution = shows the values of a variable and
often each occurred
Cumulative frequency = obtained by adding frequencies one
at a time across a row of frequencies
e.g. frequency 1 4 8...
cumulative frequency 1 15 13...
Stem and Leaf diagram = each row represents a stem and is
indicated by the number to the left of the vertical line. The
to the right of the vertical line are leaves associated with the
5 0 1 1 2 4
6 0 1 2 6
7 1 2 4 8
Grouped frequency distribution = a table in which frequencies
are associated with groups or classes rather than single
Terminology = consider the class 810
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Lower class boundary = 7.5
Lower class limit = 8
Class midpoint = 9
Upper class limit = 10
Upper class boundary = 10.5
Class width = 3
Histogram = used to represent a continuous variable which
been summarised by a group frequency distribution. Each
or class is represented by a bar with width equal to the class
width and area proportional to its frequency.…read more