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# presentation4 - CHAPTER 4 Probabilities and Research The...

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Unformatted text preview: CHAPTER 4 Probabilities and Research: The Risks and Rewards of Scientific Sampling Samples and Their Populations: Why Statisticians Are Stingy! Decision making The risks and rewards of sampling Risks 1. The sample might not represent the larger population. 2. We might not know that the sample is misleading. 3. We might reach inaccurate conclusions. 4. We might make decisions based on this bad information. Benefits 1. The sample represents the larger population. 2. We increase our level of confidence in our own findings. 3. We reach accurate conclusions at a very low cost. 4. We remain open-minded because we know samples can mislead us. 5. We make wiser decisions based on the available evidence. Random sampling Every member of the population has an equal chance of being selected in our study Expensive, time-consuming, and often impossible Convenience Sample A convenience sample is one that uses participants who are readily available. Variations on random sampling Cluster sampling Is a variation of random sampling in which all of the clusters in a population are identified, a certain number of clusters are selected randomly, and everyone in the cluster is recruited to participate. Stratified sampling Where strata (usually levels of nominal variable) are identified and then a random sample of the same size is taken from each strata sample Variations on random sampling Convenience sampling: limits our external validity. Replicate our study Volunteer of self-selected samples: these are convenience samples in which participants actively choose to participate. Random assignment An equal chance of being assigned to a condition...
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• Fall '10
• Fairchild
• Null hypothesis, Statistical hypothesis testing, random assignment, Type I and type II errors, random sampling

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presentation4 - CHAPTER 4 Probabilities and Research The...

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