lecture2ccle - Observational Studies Experiments Statistics...

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Observational Studies & Experiments Statistics 10 - Lecture 2 VIVIAN LEW UCLA DEPARTMENT OF STATISTICS SPRING 2015
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Last Time Recall - scientific inquiry begins with a question The next step: data collection
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Collecting Data Method 1: minimal intervention on the part of the researcher, data arises naturally and is recorded. Can demonstrate association with this data, but unable to convincingly show causality. Method 2: active and deliberate intervention by the researcher, data might be created in a manner which may seem artificial or unrealistic. Primarily used to investigate/establish causality.
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Method 1: Observational Studies An Observational Study utilizes pre-existing groupings (groups are determined by the treatment of interest and were not created by the scientist) and simply records the outcomes between the groups. In an observational study, if an outcome occurs more often with one of the groups than with the other, we believe that the treatment and outcome are associated.
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Problem: Association Causation in observational studies Does this mean that countries that want more Nobel Prizes should consume more chocolate? No. Chocolate is a confounding variable (obscures the truth)
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Problem: Association Causation in observational studies If the author had chosen luxury cars ownership instead of chocolate… We get a similar picture, clearly they are related but do luxury cars CAUSE Nobel Prizes?
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OBSERVATIONAL STUDY DESCRIBE THE NATURE OF THE ASSOCIATION BETWEEN EDUCATION AND INCOME
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Method 2: Experiments An Experiment involves the deliberate assignment of participants into one of at minimum two groups, then the administration of a treatment and a recording of the outcomes between the groups. When participants are randomly assigned to their groups, this is a randomized experiment. The randomized experiment has fundamental importance in science.
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DR. LIND & THE FIRST MODERN EXPERIMENT
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Elements: Controlled Experiments A controlled experiment is an experiment where each subject is assigned to either a control group (baseline) or a treatment group. The sample sizes should be large enough to account for other variability (e.g., health, IQ).
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