Statistical Tests

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  • Created by: mollyb
  • Created on: 13-06-13 15:19
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  • Statistics
    • Mean
      • add the quantities together and divide by the number of quantities
      • Most useful but requires calculation
      • Distorted by extreme values and involves calculation
    • Median
      • the central value when values are put in order
      • gives no idea of other values
    • Mode
      • the value that occurs most frequently
      • gives no idea of other values
    • Range
      • difference between the highest and the lowest
      • misleading if their are abnomalies
    • Interquartile Range
      • difference between the inner half around the mean
      • quick and easy to calculate
      • ignores values above and below this
    • Standard Deviation
      • shows a spread of all values around the mean
      • uses a formula and calculation and distorted by extreme values
      • larger the S.D the larger the variation
      • uses when comparing similar means
    • Mann Whitney U
      • compares medians and ranks them to see if data sets differ
      • Disadvantage: uses a formula and calculation making working out difficult and uses a significance tables
      • Tests for a difference and starts by assuming that both sets of data are alike and then establishes whether its is safe to reject assumptions
    • Chi Squared
      • Difference
        • compares observed and expected frequecies
        • uses a formula, calculation + significance table
        • how do you determine expected frequency?
      • Correlation
        • compares observed and the frequency expected given a certain hypothesis
        • uses a formula, calculation and a significance table
        • how do determine expected frequency?
    • Spearmans Rank
      • measures the strength of a relationship between two sets of ranked data
      • uses a formula and calculation
      • only uses ranks of data and significance tables
    • Skew
      • the extent to which the mode and mean differ.
      • can be positive or negative and can occur if distributions are not symmetrical
      • if the mode is lower that the mean it is said to be negatively skewed and visa versa.
    • Kurtosis
      • used to show wave length/ amplitude but shows shape
      • shows shapes such as wavelength and distributions can be flat or in between.
  • Tests for a difference and starts by assuming that both sets of data are alike and then establishes whether its is safe to reject assumptions

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