Data Lab #6 July 9, 2008 Ivan Katchanovski, Ph.D. POL 242Y-Y

Correlation: SPSS Commands SPSS Command: Analyze-Correlate-Bivariate-Pearson Research Hypothesis: The level of economic development has a positive effect on the level of democracy Dataset: World Variables: – Freedom House democracy rating reversed: Dependent variable Interval-ratio – GDP per capita ($1000): Independent variable Interval-ratio 2

Example: Interpretation Pearson Correlation Coefficient:.607 – Positive association in expected direction – Strong association Statistical significance SPSS: p(obtained)=.000 <p(critical)=.001=.1% Statistically significant at the.001 or.1% level Research hypothesis: supported by correlation analysis – The level of economic development has a positive and statistically significant effect on the level of democracy 3

Scatterplot: Example SPSS commands: Graphs-Interactive-Scatterplot Assign variables: – Vertical axis box: select the dependent variable Freedom House democracy rating reversed – Horizontal axis box: select the independent variable GDP per capita ($1000) – Double click to edit scatterplot Positive association between the economic development level and the democracy level

Scatterplot: SPSS Graph Example 5

Correlation Matrix Correlation Matrix: correlations of more than 2 variables Example: The Greatest Portuguese vote reliability check – Variables: TV vote, Poll 1, Poll 2 – TV vote is weakly correlated with Poll 1 and Poll 2 – Correlations of TV vote with Poll 1 and Poll 2 are statistically insignificant – Poll 1 and Poll 2 are strongly correlated – Correlation between Poll 1 and Poll 2 is statistically significant at the.05 level TV vote data are not reliable measure of public opinion concerning “Greatest Portuguese” Public opinion polls are reliable measure of public opinion concerning “Greatest Portuguese” 6

Greatest Portuguese: SPSS Correlation Matrix TV votePoll No 1Poll No 2 TV votePearson Correlation Sig. (2-tailed) N10 Poll No 1Pearson Correlation (*) Sig. (2-tailed) N10 Poll No 2Pearson Correlation (*)1 Sig. (2-tailed) N10 7 * Correlation is significant at the 0.05 level (2-tailed).

Correlation Matrix: Table TV votePoll No 1Poll No 2 TV vote 1 Poll No Poll No ***1 8 Table 1. Correlation Matrix *** Correlation is significant at the level.