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Data Lab # 2 Descriptive Statistics May 28, 2008

Learn about measures of central tendency like mode, median, and mean in SPSS, alongside graphical displays such as bar charts, pie charts, histograms, and more. Explore skewness of distributions and advanced SPSS options for variable management.

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Data Lab # 2 Descriptive Statistics May 28, 2008

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  1. Data Lab # 2Descriptive StatisticsMay 28, 2008 Ivan Katchanovski, Ph.D. POL 242Y-Y

  2. Measures of Central Tendency: The Mode • The mode is the only measure of central tendency for nominal variables • The mode can also be found for ordinal and interval-ratio variables • Example: select a nominal variable • colony (World dataset) • SPSS Command: • Analyze-Descriptive Statistics-Frequencies-Statistics-Mode • Identify the mode by a value in statistics box • Identify the mode by a value with the highest frequency • Identify the mode by a value with the highest percentage in “valid percent” column

  3. Measures of Central Tendency: The Median • The median is appropriate for ordinal and interval-ratio variables • The median is not appropriate for nominal variables • Example: Select an ordinal variable • Economic development (World dataset) • SPSS Command: • Analyze-Descriptive Statistics-Frequencies-Median • Identify the median by a value in statistics box • Identify the median by a value below which 50% of cases lie in “cumulative percent” column

  4. Measures of Central Tendency: The Mean • The mean is only appropriate for interval-ratio variables • Example: Select interval ratio variable • GDP per capita $1000 (World dataset) • SPSS Command: • Analyze-Descriptive Statistics-Frequencies-Statistics-Mean • Identify the mean by a value in statistics box

  5. Graphic Description of Variables: Bar Chart • Bar chart • Most appropriate for nominal and ordinal variables • Shows dispersion of a variable • Example: select a nominal variable • colony (World dataset) • SPSS Commands: • Analyze-Descriptive Statistics-Frequencies-Charts-Bar charts-Percentages • Open Chart Editor: Select chart-Edit-SPSS Chart Object-Open • In Chart Editor: Options-Title • In Chart Editor: Elements-Show Data Labels

  6. Graphic Description of Variables: Pie Chart • Pie chart • Most appropriate for nominal and ordinal variables with small number of values (categories) • Example: select an ordinal variable • economic development (World dataset) • SPSS Commands: • Analyze-Descriptive Statistics-Frequencies-Charts-Pie charts-Percentages • Open Chart Editor: Select chart-Edit-SPSS Chart Object-Open • In Chart Editor: Options-Title • In Chart Editor: Elements-Show Data Labels

  7. Graphic Description of Variables: Histogram • Histogram • Most appropriate for interval-ratio variables with large number of values • Shows dispersion of a variable • Example: select an interval-ratio variable • GDP per capita $1000 (World dataset) • SPSS Commands: • Analyze-Descriptive Statistics-Frequencies-Charts-Histograms • Open Chart Editor: Select chart-Edit-SPSS Chart Object-Open • In Chart Editor: Options-Title • In Chart Editor: Elements-Show Data Labels

  8. Skewness of Distributions • Skewness of distributions • Appropriate for interval-ratio variables • Example: select an interval-ratio variable • GDP per capita $1000 (World dataset) • SPSS Commands: • Analyze-Descriptive Statistics-Frequencies-Statistics-Skewness/Mean/Median • Unskewed distribution if skewness statistics=0 or mean=median • Positively skewed distribution if skewness statistics>0 or mean>median • Negatively skewed distribution if skewness statistics<0 or mean<median

  9. Helpful SPSS Options • SPSS option for displaying variable labels instead of variable names • Open the 2000 World Values Survey Dataset • Edit-Options-General-Display labels • SPSS option for selecting cases • Example: selecting Canadian respondents from the World Values Survey dataset • Identify value for Canada (12) in “nation” variable (v2) • Data-Select cases-If: v2=12

  10. Dependent and independent variables • Describing dependent and independent variables • The 2000 World Values Survey • Questionnaires • Country specific questionnaires online at http://www.worldvaluessurvey.org/ • “Documentation of the Values Surveys” & “1999-2004 wave” • Select Canadian questionnaire and Canadian sample of the 2000 World Values Survey dataset • Identify dependent variable • Identify independent variable • Produce appropriate descriptive statistics and charts

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