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S519: Evaluation of Information Systems

S519: Evaluation of Information Systems. Social Statistics Ch4: Chart. Chart. Label everything One graph communicate one idea Keep things balanced Simple is best A picture is worth a thousand words. Frequency distribution.

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S519: Evaluation of Information Systems

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  1. S519: Evaluation of Information Systems Social Statistics Ch4: Chart

  2. Chart • Label everything • One graph communicate one idea • Keep things balanced • Simple is best • A picture is worth a thousand words

  3. Frequency distribution • Frequency distribution is a method to represent the frequency of certain scores. • When you have a data set, such as a testing scores, • Class intervals • Number of intervals: 5, 10, 20 • Value of interval=range/number of intervals

  4. Exercise • 50 scores • Set class intervals • Create a histogram using your hand • Using Excel to do that

  5. A histogram

  6. Excel for Histogram • First, define your bins • The starting point of a bin • Data analysis Toolpak  histogram

  7. Skewness • Skewness (S-p98-Fig 4.15) • Measure of the lack of symmetry of a distribution • mean>median>mode  positively skewed • mean<median<mode  negatively skewed

  8. Kurtosis • Kurtosis (S-p99-Fig 4.16) • flat or peaked of a distribution

  9. Variability • Variability (S-p97-Fig 4.14)

  10. Frequency distribution • Excel: SKEW() and KURT() • As a general rule, we will conclude that the distribution is significantly skewed or kurtotic if the statistic is greater than three times its standard error. • For example, your rule to determine if the distribution is actually skewed (to confirm your visual impression) is:  IF skew > ± 3 * SE_Skewness THEN it is skewed. • SPSS can do this

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