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| a description of hte approach that will be used to btain samples from a population prior to any data collection activity |
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| the list from which the sample is selected |
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| involves selecting items from a population so that every subset of a given size has equal chance of being selected |
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| uses expert judgment to select the sample |
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| samples are selected basaed on the ease with which the data can be collected |
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| systematic period sampling |
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selects items periodically from the population
ex. every 25 names |
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applies to populations that are divided into natural subsets (strata) and allocated teh appropriate proportion of samples to each stratum
ex. large city divided into political wards/districts |
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based on dividing a population into subgroups (clusters), sampling a set of clusters, and (usually) confiction a complete census within the clusters sampled
ex.all customers in one geographic region |
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| sampling from a continuous process |
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Definition
selecting a sample from continuous manufacturing process can be accomplished in 2 main ways:
- select a time at randome; then select the next n items produced after that
- select n times at ramdon; then select the next item produced after these times
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Definition
| occurs when a sample does not represent the target population adequately |
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| sampling (statistical) error |
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| occurs because samples are only a subset of the population |
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| invloves assessing the value of an unkown populaton parameter (ex. mean) using sample data |
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| single numbers used to estimate the value of a population parameter |
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| confidence nterval estimates |
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Definition
| provide a range of values between which the valie of hte population parameter is believed to be, and alos provide an assessment of sampling error by specifying a probability that the interval correctly estomates the true (unknown) population parameter |
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Definition
| if the expected value of an estimator equals the population parameter it is intended to estimate |
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| if the expected value of an estimator is not equal to the population parameter it is intended to estimate |
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| provides a range within which we believe the true population parameter falls |
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| an interval estimate that also specifies the likelihood that hte interval contains the true population parameter |
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| also known as the confidence interval |
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a family of probability distributions with a shape similar to the standard normal distribution
have an additional parameter: degrees of freedom |
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Definition
makes the t-distribution unique?
when df is high it looks like anormal distribution, as df decreases the curve levels out |
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Definition
| an nbaised estimator of a population proportion pi |
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Definition
characterized by degrees of freedom
not normal |
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Definition
| desribes the probability that random variable falls w/i the interval and is often used in desribing risk |
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