Empirical Research Methods

Transcription

1 Institut für Politikwissenschaft Schwerpunkt qualitative empirische Sozialforschung Goethe-Universität Frankfurt Fachbereich 03 Prof. Dr. Claudius Wagemann Empirical Research Methods 25 June 2013 Quantitative Data Analysis and Statistics

2 Advantages of Secondary Analysis Cost Time High-quality data Better opportunities for longitudinal analyses Easier differentiation of sub-groups Easier differentiation of countries More time for data analysis More possibilities for moving between ideas and evidence Empirical Research Methods 2

3 Disadvantages of Secondary Analysis Lack of familiarity with data Complexity of data No control over data quality Potential absence of key variables Empirical Research Methods 3

4 Statistics: Levels of Variables Nominal (categorical) variables Binary, binomial, dichotomous Multinomial Ordinal variables Interval+ variables Interval only Ratio Absolute scales Empirical Research Methods 4

5 Simple Forms of Statistical Analysis Distributions Frequencies Graphs and diagrams Empirical Research Methods 5

6 Tukey, Exploratory Data Analysis Empirical Research Methods 6

7 Schnell, Graph-Based Data Analysis Empirical Research Methods 7

8 Different Diagrams Bar charts (vertical and horizontal) Histogram Pie chart Functions, graphs, lines Scatter plot Spider chart Empirical Research Methods 8

9 Different Diagrams Bar charts (vertical and horizontal) Histogram Pie chart Functions, graphs, lines Scatter plot Spider chart Empirical Research Methods 9

10 Different Diagrams Bar charts (vertical and horizontal) Histogram Pie chart Functions, graphs, lines Scatter plot Spider chart Empirical Research Methods 10

11 Different Diagrams Bar charts (vertical and horizontal) Histogram Pie chart Functions, graphs, lines Scatter plot Spider chart Empirical Research Methods 11

12 Different Diagrams Bar charts (vertical and horizontal) Histogram Pie chart Functions, graphs, lines Scatter plot Spider chart Empirical Research Methods 12

13 Different Diagrams Bar charts (vertical and horizontal) Histogram Pie chart Functions, graphs, lines Scatter plot Spider chart Empirical Research Methods 13

14 Different Diagrams Bar charts (vertical and horizontal) Histogram Pie chart Functions, graphs, lines Scatter plot Spider chart Empirical Research Methods 14

15 Statistical Moments First moment: measures of central tendency Mode Median Artihmetic mean Second moment: measures of dispersion Variance Standard deviation Third moment: measures of skewedness Fourth moment: measures of curtosis Empirical Research Methods 15

16 Levels of Variables and Bivariate Analysis x / y Nominal Ordinal Intervall+ Nominal Cross-Tabulations ², ²,, Cramér s v Tests by Wilcoxon and Mann/Whitney (2 groups) Tests by Friedman and Kruskal/Wallis (> 2 groups) t test (2 groups) Analysis of Variance (ANOVA, > 2 groups) Ordinal Various parameters (Spearman s, Kendall s ) Intervall+ Logistic Regression (LOGIT, PROBIT, TOBIT) Ordinal Logistic Regression Regression (Bravais & Pearson) Correlation Empirical Research Research Design Methods 16

17 The Problem of the Judge Judgment: not guilty Judgment: guilty Reality: not guilty No problem Huge problem Reality: guilty Not so huge a problem No problem ( Power ) Empirical Research Research Design Methods 17

18 The Problem of the Judge Judgment: not guilty Judgment: guilty Reality: not guilty No problem Probability must be small!! Reality: guilty Not so huge a problem No problem ( Power ) Empirical Research Research Design Methods 18

19 The Problem of the Statistician Judgment: H 0 accepted Judgment: H 0 rejected Reality: H 0 accepted No problem Huge problem Reality: H 0 rejected Not so huge a problem No problem ( power of the test ) Empirical Research Research Design Methods 19

20 The Problem of the Statistician Judgment: H 0 accepted Judgment: H 0 rejected Reality: H 0 accepted Alpha error Level of significance Reality: H 0 rejected Beta error Empirical Research Research Design Methods 20