Introduction to Producing Data Lesson 5 - I Introduction to Producing Data

Objectives Knowledge Objectives: Students will: Explain the difference between an observational study and an experiment.   Construction Objectives: Students will be able to: Give some examples of studies, and classify each as either an observational study or an experiment.

Vocabulary Observational Study – variables are measured (but not controlled); no attempt to influence the response Experiment – variables are measured and “treatments” are imposed on some variables (these variables are controlled); these “treatments” are attempts to influence the response Sample – a small group used to represent the much larger population

Studies vs Experiments Observational Studies cannot determine cause and effect Experiments can possibly determine cause and effect

Observational Studies Draws inferences about the possible effect of a treatment on subjects, where the assignment of subjects into a treated group versus a control group is outside the control of the investigator Observational studies infer possible causes (basis of future experiments), but cannot determine cause and effect Experiments may be beyond the control of the investigator for a variety of reasons: A randomized experiment would violate ethical standards The investigator may simply lack the requisite influence A randomized experiment may be impractical From Wikipedia, the free encyclopedia

Experiments Method of investigating causal relationships (cause and effect) among variables, or to test a hypothesis Often the experimenter is interested in the effect of some process or intervention (the "treatment") on some objects (the "experimental units"), which may be people, parts of people, groups of people, plants, animals, etc. A controlled experiment generally compares the results obtained from an experimental sample against a control sample, which is practically identical to the experimental sample except for the one aspect whose effect is being tested (the independent variable). From Wikipedia, the free encyclopedia

Summary and Homework Summary Homework Observational Studies Observe and measure variables No cause and effects can be inferred Experiments Some variables are controlled to see the effect on the response Cause and effect may be illustrated Homework none