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Coursework Notes - Information


Representing Data


bar/block graph

pie chart

scatter diagram

stem & leaf table



Bar/block graph


block graph


Not to be confused with a histogram, a bar chart/graph has columns of equal width, with height representing some variable, usually a number(eg frequency, % money).


The base of each column can represent anything (eg a car type, a person's name, a company).

Unlike a histogram, in a bar graph the columns need not be adjacent to eachother .




Pie Chart


One sweep of the circle 360 degrees, represents the whole.


Percentages are represented by different angles, like slices of a pie/cake.


In our example the angle in degrees for each car make is given by:



'% import' x 360




pie chart



car make

% imports into country X













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Scatter diagrams/graphs



scatter diagrams



When two sets of data are plotted against eachother, a scatter of points is produced.


Correlation is the relationship between one set of data and the other.


An exact correlation would be '1' (a straight line graph with all the points on the line), while a zero correlation is '0'.


The first graph would have a correlation between 0 and 1.


The second graph would have a correlation between 0 and -1.


The third graph would have a correlation close to zero.




Stem & Leaf table


Stem & leaf tables are similar to bar charts but differ in two distinct ways:



  1. The pattern is horizontal, not vertical.

  3. The display is made from numbers, not block colour.

  5. The data is placed in number order in groups of tens. It is then displayed horizontally for each tens grouping, starting with 0-9 at the top.



stem and leaf #1



The numbers displayed are:




11   13   15


20   24   24   26   29


34   36   38   38   39   39   39


47   48   49   49   49


51   51   53   54   58   59


60   61   61   62


73   74   75





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