Block 2 Revision

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Block 2 Revision

• By Meera

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Contents

• Stem and Leaf diagrams
• Cumulative Frequency graphs
• Variance
• Standard Deviation and Standardised Scores

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Stem and Leaf diagrams

• These show the raw data in a neat and readable
  format.
• We can easily use the information given to create
  other statistical diagrams.
• 5 points that we can read of the diagram are the
  Minimum, the Lower quartile, the Median, the
  Upper quartile and the Maximum
• Numbers after the Stem should all be in line
  (vertically)
• Numbers after the Stem should all be in order,
  smallest first.
• Stem and Leaf diagrams always need a title and a
  key.

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Cumulative Frequency graphs

• Cumulative means the total so far
• All Cumulative Frequency graphs create a
  Sigmoidal shape.
• From these graphs you can read of the 5 points.
• You can then also draw other charts after drawing
  the Cumulative Frequency
• For example Box and Whisker Plots

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Variance

• The Variance shows us the spread of the data.
• It also tells how far the data is from the mean.
• The Variance uses ALL the data
• S(x-x)2
• n
• X Variable, X mean of x

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Standard Deviation and Standardised Scores

• Standard deviation is the square root of the
  Variance.
• S(x-x)2
• n
• Standardised Scores help us compare different
  sets of data to each other
• For example Maths scores to English scores and
  etc.
• To work out the standardised score we need to
  know the Mean and the Standard Deviation of the
  sets of data.
• Z xµ (Standardised Score Score Mean
  )
• s

Standard Deviation