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Types of Sampling

Types of Sampling. Simple Random Cluster Stratified Systematic (every kth element is sampled). Assumptions. Members of the Population can be numbered from 1 to N where N is the population size

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Types of Sampling

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  1. Types of Sampling • Simple Random • Cluster • Stratified • Systematic (every kth element is sampled)

  2. Assumptions • Members of the Population can be numbered from 1 to N where N is the population size • You have a mechanism for randomly picking n numbers (usually without replacement) from the collection of numbers 1,2,3,…,N • If number k is selected, the population element with that number is in the sample

  3. Simple Random Sample 1 12 17 10 6 9 • Population above right • In a Simple Random Sample each population member is equally likely to be selected • Click to sample 2 13 8 18 16 20 3 14 4 15 19 7 11 21 5

  4. 1 2 13 14 12 4 17 3 5 18 15 16 8 24 7 22 9 21 6 19 23 20 11 10 Cluster Sampling • The Population (right) can be divided into strata • A stratum consists of population elements that are similar in some way • All of one or more strata are randomly selected and used in the sample—see next slide

  5. 24 22 21 19 23 20 Population Above—Click to take a Cluster Sample 1 2 13 14 12 4 17 3 5 18 15 16 8 7 9 6 11 10

  6. 1 2 13 14 12 4 17 3 5 18 15 16 8 24 7 22 9 21 6 19 23 20 11 10 Stratified Sampling • The Population (right) can be divided into strata • A stratum consists of population elements that are similar in some way • A random sample from each stratum is randomly selected and used in the sample—see next slide

  7. Population Above—Click to take a Stratified Sample 1 2 13 14 12 4 17 3 5 18 15 16 8 24 7 22 9 21 6 19 23 20 11 10

  8. Systematic (every kth) • A starting number is randomly chosen • The population element corresponding to the starting number and every kth population element after that are selected for the sample • ‘Circular’ counting is used

  9. Every 7th Element Sample 1 12 17 10 6 9 • Population above right • Click once to get a random starting element • Click again to get every 7th element after that 2 13 8 18 16 20 3 14 4 15 19 7 11 21 5

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