Chapters 5 6 and 7

Chapters 5 6 and 7 - Chapters 5, 6, and 7 (Student)...

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Chapters 5, 6, and 7 (Student) 1 Experiments, Good and Bad • What makes some studies convincing? • Why should we ignore others? Experiments, Good and Bad • Observational studies are passive data collection. • Experiments are active data collection. • All experiments (and some observational studies) are interested in the effect one variable has on another variable. • If an experiment is properly designed, we can observe whether cause and effect relationships are present. Vocabulary of Experiments • Response Variable – a variable that measures an outcome or result of a study (variable whose changes we wish to study) • Explanatory Variable – a variable that explains or causes changes in the response variable. • Subjects – individuals studied in an experiment. • Treatment – any specific experimental condition applied to the subjects.
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Chapters 5, 6, and 7 (Student) 2 Three Studies • Online vs. Traditional Classroom – Students choose type of class – End of course exam grades compared • Gastric Freezing – All patients get freezing – Report ulcer pain relief • Government Daycare for Low-Income Children – Children split randomly – Success in school compared Example Does taking large amounts of vitamins protect against cancer? To study this question, researchers enrolled 29,000 Finnish men, all smokers over the age of 50. The men were separated into two groups randomly. Half of the men took vitamin supplements, and others took a dummy pill that has no active ingredient. The researchers followed all the men for eight years. At the end of the study, men in the vitamin group were no less likely to have cancer than men in the other group. This study cast doubt on the popular idea that taking lots of vitamins can reduce the risk of cancer. Confounding • Lurking variable – a variable that has an important effect on the relationship among the variables in a study but is not one of the explanatory variables studied. • Confounding – when the effects of two variables (explanatory or lurking) on a response variable cannot be distinguished from one another.
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Chapters 5, 6, and 7 (Student) 3 Study: Online vs. Traditional Classroom Online vs. Classroom (Explanatory Variable) Test scores after course (Response Variable) Student preparation (Lurking Variable) Causes? One – Track Experiment • Gastric Freezing – All patients get freezing – Report ulcer pain relief Randomized Comparative Experiments • Randomized Comparative Experimental Design Compare the effects of a treatment on an experimental group to a control group. – Subjects are randomly assigned to two groups – Experimental Group – The individuals/subjects on which the complete experiment is performed. – Control Group
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Chapters 5 6 and 7 - Chapters 5, 6, and 7 (Student)...

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