PSC 202 1st Edition Lecture 13 Outline of Last Lecture I. Review Outline of Current LectureI. Cross-Tabs and Mean ComparisonsII. Controlled Comparison with Cross-TabsCurrent LectureI. Cross-Tabs and Mean Comparisons- we want to create comparison groups with different values of the independent variable. Test whether dependent variable also differs across these groups- Population samplegroup A group B group C- 2 kind of tables: cross tabulation and mean comparison- cross tabulation: used when all variables are nominal or ordinal levelo compare frequencies across categories- mean comparison: used when dependent variable is interval level; others are nominal or ordinal o compare means across categoriesII. Controlled Comparison with Cross-Tabs- we fail to observe the correct relationship between x and y due to the alternative factor zThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- zero-order relationship: relationship between two variables, without controlling for any other factors- partial-effect: relationship between two variables after taking effect of other variables into account- after controlling for z, we can identify one of the following types of relationships:o spurious: there is no causal relationship between x and yo additive: the relationship between x and y is the same across different values of zo interactive: the relationship between x and y is different for different values of z- steps for interpretation:o Are all controlled effect zero or very close to it? Yes? relationship is spurious No? either additive or interactiveo Are all controlled effects approximately the same size? Yes? additive No?
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