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20 Cards in this Set
- Front
- Back
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standard deviation of the population divided by the square root of the size of the sample
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standard error
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two things which affect the standard error
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1) Size of the standard deviation
2) Size of the sample |
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as "n" increases, the underlying distribution of sample means will approach a normal distribution
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CLT
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Four Methods of Sampling which meet the requirement of randomness
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1) Random Number Tables
2) Systematic Sampling 3) Stratified Sampling 4) Cluster Sampling |
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begin with a starting point that is selected at random, and thereafter select every "ith" item
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Systematic Sample
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Advantages of systematic sample
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1) Spread more evenly
2) Easier to conduct than simple random sample |
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Disadvantage of Systematic Sample
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May interact with some hidden pattern in the population
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Rules of Stratified Sampling
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1) Must be divided into strate or homogenous subgroups using common characteristic
2) Strata must not have overlapping groups 3) May include such things as geographical areas, age groups or gender |
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Advantages of Stratification
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1) Develop greater sample precision
2) Administratively Convenient |
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When will proportion allocation be used?
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when determining the content of the sample
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useful if your population is too difficult to reach in normal ways
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Cluster Sampling
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How to Use Cluster Sampling
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1) pop. divided into clusters
2) clusters numbered and random selection of clusters is made 3) Each of the clusters is then sampled 100% |
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Examples of Clusters
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Apartment complexes
Election Districts City Blocks |
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Advantages to Cluster Sampling
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Minimize Travel Time and Expenses
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Disadvantages to Cluster Sampling
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1) Units close to eachother may be very similar and less likely to represent the whole population
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Example of Quota or Mall Intercept Sampling
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Interviewer told to sample 50 females between the age of 45 and 60
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Advantages of Quota Sampling
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Quick to organize
Inexpensive |
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Disadvantage of Quota Sampling
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Not as representative of the whole population as the other methods
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due to mistakes either intentional or unintentional
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Non-Sampling Error
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associated with business decisions that have binary results
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Proportions
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