09 1450 Chapter 9 - Chapter 9 Producing Data Experiments STAT 1450 Autumn 2014 9.0 Producing Data Experiments Connecting Chapter 9 to our Current

09 1450 Chapter 9 - Chapter 9 Producing Data Experiments...

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Chapter 9: Producing Data: Experiments STAT 1450 – Autumn 2014
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Connecting Chapter 9 to our Current Knowledge of Statistics Chapter 8 focused on data collection through sampling. There were two primary classes of sampling: scientific and non-scientific. But, ultimately we were able to collect data via question posing and analyzing the responses. We will now collect data without using questioning techniques. 9.0 Producing Data: Experiments
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Observation vs. Experiment An observational study focuses on individuals and measures variables of interest but does not attempt to influence the responses. Data is collected to better describe a group or situation. There is no active treatment being impressed upon the individuals. An experiment , on the other hand, deliberately imposes some treatment on individuals in order to observe their responses. 9.1 Observation vs. Experiment
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Important Terminology Two variables (explanatory variables or lurking variables) are confounded when their effects on a response variable cannot be distinguished from each other. 9.1 Observation vs. Experiment
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Note 1. Observational studies are not as effective at showing cause and effect because of confounding. 2. Confounding can happen in experiments, but ideally the researcher designs the experiment to avoid confounding. 9.1 Observation vs. Experiment
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Subjects, Factors, and Treatments The individuals studied in an experiment are often called subjects , particularly when they are people. Animals or objects can be subjects also. The explanatory variables in an experiment are often called factors . A treatment is any specific experimental condition applied to the subjects . If an experiment has more than one factor, a treatment is a combination of specific values of each factor. 9.2 Subjects, Factors, and Treatments
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Example Crohn’s disease is a bowel disease that causes cramping abdominal pain, fever, and fatigue. A study reported in the New England Journal of Medicine (Columbel et al., 2010) test two medicines for the disease: injections of infliximab (Inflix) and orel azathioprine (Azath) The participants were randomized into three groups. All groups received an injection and a pill (some were placebos, but still a pill and an injection). One group received Inflix injections alone (with placebo pills), one received Azath pills alone (with placebo injections), and one group received both injections and pills. A good outcome was defined as the disease being in remission after 26 weeks. Assume that there were 170 participants in each group. (Source: Example 9, Chapter 1, Introductory Statistics: Exploring the World Through Data , Gould and Ryan, 2013.) Identify the individuals/subjects. 9.2 Subjects, Factors, and Treatments
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Example Crohn’s disease is a bowel disease that causes cramping abdominal pain, fever, and fatigue. A study reported in the New England Journal of Medicine (Columbel et al., 2010) test two medicines for the disease: injections of infliximab (Inflix) and orel azathioprine (Azath) The participants were randomized into three groups. All groups received an
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  • Spring '15
  • MichelleDuda
  • Statistics, placebo, Randomized Comparative Experiments

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