prelim 2 sheet

# prelim 2 sheet - Chapter 6 Standard Deviation as a Ruler...

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Chapter 6: Standard Deviation as a Ruler and the Normal Model z= (y – y bar)/s -Adding or subtracting a constant amount to each value just adds or subtracts the constant to the mean, median, quartiles, max and min. The IQR, SD, or range do not change. -Dividing or multiplying by a constant amount causes the mean, median, range, IQR, and SD to be divided or multiplied by that same value. -normal models are appropriate for distributions that are unimodal and roughly symmetric - Don’t use normal models when the distribution isn’t unimodal and symmetric- draw a histogram or probability plot Skewed Right: mean > median Skewed left: Median > mean Chapter 12: Sample Surveys Sample: group selected from the population Sample survey: asking questions of a small group of people in hope of learning something about the population Biased: a sample that does not represent the population in some important way -randomizing protects us from the influences of all the features of our population. It makes sure that the sample usually looks like the rest of the population. Population parameter: numerically valued attribute of a model for the population Simple random samples: each set of elements in the population has an equal chance of selection Sampling frame: list for individuals from which the sample is drawn Census: a sample that consists of the entire population Stratified random sample: the population is divided into several subpopulations (strata), and random samples are then drawn from each stratum. Cluster: entire groups, or clusters, are chosen at random. Each cluster should be heterogeneous, and al the clusters should be similar to each other. Systemic sample: selecting individuals systematically from a sampling frame Multistage sample: sampling schemes that combine several sampling methods Voluntary response bias: individuals can choose on their own whether to participate Convenience sample: individuals who are conveniently available Undercoverage: fails to sample from some part of the population Nonresponse bias: when a large fraction of those sampled fail to respond Response bias: anything in a survey design that influences responses i.e.- wording of a question Sampling variability: the natural tendency of randomly drawn samples to differ, one from another. Sometimes called sampling error Chapter 13: Experiments Observational study: no manipulation Retrospective study: observational study in which subjects are selected and then heir previous condition or behaviors are determined. Prospective study: an observational study in which subjects are followed to observe future outcomes Factor: a variable whose levels are controlled by the experimenter Experimental units: individuals on whom an experiment is performed Treatment: the process, intervention, or other controlled circumstances applied to randomly assigned experimental units Control- aspects of the experimental that we know may have an effect on the response, but that are not the factors being studied Principles of experimental design: control; randomize; replicate; block

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