Gathering Data and Probability S07

Gathering Data and Probability S07 - STAT E-50 -...

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STAT E-50 - Introduction to Statistics Gathering Data; Probability 1. Ten percent of us are left-handed. In a study of dexterity, people are randomly selected in groups of five. Use Table E to develop a simulation for finding the probability of getting at least one left-handed person in a group of five. What is the component to be repeated? How will you model the outcome? How will you simulate the trial? What is the response variable? Run several trials: Trial number Outcomes At least one? 1 2 3 4 5 6 7 8 9 10 Page 1
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Samples and Populations ± Choose a random sample to avoid bias, to be sure that your sample is representative of the population. ± In a representative sample, the statistics reflect the corresponding parameters accurately. ± In a Simple Random Sample , each sample of the size you want has an equal chance of being chosen. ± Determine a sampling frame , and choose your sample randomly from it. ± There will always be sampling variability between samples. Sampling Designs Stratified Sampling: the population in broken into homogeneous strata , and simple random sampling is used within each stratum. Cluster Sampling: divide the population into similar clusters , then choose clusters at random and complete a census on each Multistage Sampling: a combination of sampling methods. Systematic Sampling: start with a randomly selected subject, then systematically choose every k th subject from a list. What Can Go Wrong? ± Voluntary response samples ± Convenience sampling ± Incomplete sampling frames ± Undercoverage ± Nonresponse bias ± Response bias ± Surveys that are difficult to complete Page 2
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2. Which kind of sampling (random, stratified, systematic, cluster, convenience) is used in each of the following examples? a. A marketing expert for MTV is planning a survey in which 500 people will be randomly selected from each age group of 10 -19, 20-29, etc. b. An ABC reporter polls people as they pass him on the street. c. A Johns Hopkins University researcher surveys all cardiac patients in each of 30 randomly selected hospitals. d.
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Gathering Data and Probability S07 - STAT E-50 -...

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