{"schemaVersion":2,"id":"iv2sls","title":"Instrumental Variables & 2SLS","totalStages":31,"modules":[{"id":"iv2sls-why-ols-fails","title":"1 · Why OLS fails","summary":"Endogeneity from omitted variables and simultaneity makes OLS biased and inconsistent.","stageCount":6,"stages":[{"id":"iv2sls-why-ols-fails-01","index":0,"moduleId":"iv2sls-why-ols-fails","moduleIndex":0,"type":"read","title":"The exogeneity assumption","skillIds":["iv2sls.endogeneity"],"estimatedMinutes":6,"difficulty":"applied","points":5},{"id":"iv2sls-why-ols-fails-02","index":1,"moduleId":"iv2sls-why-ols-fails","moduleIndex":1,"type":"read","title":"The sign and size of the bias","skillIds":["iv2sls.instrument-relevance"],"estimatedMinutes":6,"difficulty":"applied","points":5},{"id":"iv2sls-why-ols-fails-03","index":2,"moduleId":"iv2sls-why-ols-fails","moduleIndex":2,"type":"code","title":"Watch OLS miss the 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x).","stageCount":8,"stages":[{"id":"iv2sls-instruments-01","index":6,"moduleId":"iv2sls-instruments","moduleIndex":0,"type":"read","title":"What is an instrument?","skillIds":["iv2sls.exclusion-restriction"],"estimatedMinutes":6,"difficulty":"applied","points":5},{"id":"iv2sls-instruments-02","index":7,"moduleId":"iv2sls-instruments","moduleIndex":1,"type":"read","title":"Why both conditions are indispensable","skillIds":["iv2sls.first-stage"],"estimatedMinutes":6,"difficulty":"applied","points":5},{"id":"iv2sls-instruments-03","index":8,"moduleId":"iv2sls-instruments","moduleIndex":2,"type":"code","title":"See relevance vs exclusion in the data","skillIds":["iv2sls.exclusion-restriction"],"estimatedMinutes":10,"difficulty":"applied","points":10},{"id":"iv2sls-instruments-04","index":9,"moduleId":"iv2sls-instruments","moduleIndex":3,"type":"interactive","title":"Relevance 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