Comparative Qualitative Research Methods Oxford University, Hilary Term 2006 Wk 6: Case Selection and Research Design

1. Comparative Qualitative Research MethodsOxford University, Hilary Term 2006Wk 6: Case Selection and Research Design Adrienne LeBas Nuffield College, Oxford Email: adrienne.lebas@nuffield.ox.ac.uk Phone: 01865 278518

2. Case Studies and Qualitative Methods

3. Mill�s Methods and the Value of Individual Observations

4. Mill�s Methods and the Value of Individual Observations

5. Assumptions behind Mill and KKV Causal homogeneity: variables� causal effects are deterministic Independence of observations: observations are not affected by one another �Conditional independence� (RSI: 31-36): variation within groups with different DV values otherwise similar; if not, researcher introduces controls Non-endogeneity: variables not affected by one another

6. Selection Bias and Causal Inference

7. Selection Bias and Causal Inference

8. Selection Bias and Causal Inference

9. Selection Bias and Causal Inference: Truncation

10. KKV Advice on Case Selection Increase number of observations Full universe of cases, full range of variation Avoid selection on the dependent variable Limit number of explanatory variables: �most similar� research design According to KKV, Geddes and others, small-N research designs are particularly vulnerable to selection bias / sampling error

11. Qualitative Research and Case Selection Selection on DV is common Research designs based on �extreme values� of particular variables often useful Attempts to boost N may lead to other problems, poor estimation of causal effects Using full universe of cases imposes heavy burden for data collection, especially if question is new or understudied