203ch10_slides.pptx - STAT 203 Chapter 10 Experiments and...

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STAT 203 Chapter 10 Experiments and Observational Studies Observational Studies vs. Experiments There are two main types of studies: 1. Observational study: Consider a study which investigates the relationship between learning music and academic performance in school – a study involving elementary school children found that students who take music lessons have a better average school grade than those who do not take music lessons. The study investigators also collected information on the children (age, gender, number of siblings, etc) as well as their parents (age, income, marital status, etc). Eugenia Yu, UBC Department of Statistics. Not to be copied, used, or revised without explicit written permission from the copyright owner. 1
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STAT 203 This is an observational study. The two variables whose association is to be examined are “music learning” (explanatory variable) and “school performance” (response variable). The investigators had no control over whether or not the children take music lessons. The group that do not take music lessons serves as the control group (baseline group for comparison). In an observational study, there is no deliberate human intervention as to the individuals’ exposure to a certain condition (music learning). Sample surveys are one kind of observational study. Eugenia Yu, UBC Department of Statistics. Not to be copied, used, or revised without explicit written permission from the copyright owner. 2
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STAT 203 For the study, if individuals taking or not taking music lessons are first identified and their school marks and demographic information are then retrieved, this is a retrospective study. In contrast, if the individuals are followed over time, and we observe whether a certain outcome occurs during the course of followup, this will be a prospective study. Eugenia Yu, UBC Department of Statistics. Not to be copied, used, or revised without explicit written permission from the copyright owner. 3
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STAT 203 2. Experiment: Consider a study in which the effect of a new antihypertensive drug is to be assessed. The researcher plans to test the drug on some hypertensive patients. He will also administer the existing drug to some other hypertensive patients. Eligible patients participating in the study will be randomly assigned to one of the two drug groups. This is an experiment, which differs from an observational study in the sense that an experiment involves planned intervention on the exposure to a condition (drug type) suspected of altering the response outcome (blood pressure). We need to compare the new drug to the existing drug in order to tell if the new drug is “better”. Here, the existing drug group serves as the control group. Eugenia Yu, UBC Department of Statistics. Not to be copied, used, or revised without explicit written permission from the copyright owner.
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  • Winter '18
  • EugeniaHoiYinYu
  • Eugenia Yu, UBC Department of Statistics

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