Statistical Diagrams

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Statistical Diagrams
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Most of these will be familiar to you ..

• I hope!

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All the data used in this presentation relates
to.

• Grade C and higher in maths at G.C.S.E. at
  Hessle High School for B band students

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Pictograms

• Uses pictures or symbols
• Must have a title.
• Must have a key.
• Not always easy to read accurately.
• Not the best choice for able mathematicians like
  yourselves.

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Number of grade C or above passes in maths (B
band)

• 1999 KEY
  
• 2000 Represents
  2 people
• 2001
• 2002
• 2003
• 2004
• 2005

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Bar Charts

• Must have
• Title
• Labelled axes
• Bars should not touch unless you are dealing with
  continuous (grouped data).
• Still a little basic for you people.

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Number of grade C or above passes in maths (B
band)

• 32
• 28
• 24
• 20
• 16
• 12
• 8
• 4
• 0
• 1999 2000 2001 2002 2003
  2004 2005

F R E Q U E N C Y
YEAR
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Sneaky advertising trick!

• If you dont start your vertical axis at zero, it
  sometimes makes your data look very impressive.

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Such as
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Frequency Polygon

• Easy to draw, just put a mark at the top (in the
  middle) of each bar and join with straight lines.
• Good for comparing sets of data

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Number of grade C or above passes in maths (B
band)

• 32
• 28
• 24
• 20
• 16
• 12
• 8
• 4
• 0
• 1999 2000 2001 2002 2003
  2004 2005

x
F R E Q U E N C Y
x
x
x
x
x
x
YEAR
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Pie Charts

• Always look good
• Problems include
• Often have to round the angles so we can draw
  them.
• Slices with no entries (2002 for our data)
  dont register

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How to draw pie charts

• First find out how many degrees represent one
  person.
• 360 48 7.5

Total number of people
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Now we need a table
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Pie Chart to show GCSE grade C and above in Maths
(band B)
1999
2000
2001
2003
2005
2004
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Pie charts are very useful if ..

• ...you only have a few results and dont want to
  let on about it.
• .or, you have a large amount of data and want to
  hide something.

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These are not the only diagrams you will need to
know.

• We also need to look at
• Stem and leaf
• Cumulative frequency
• Box and Whisker.