Stratified sampling examples
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===Example 1=== | ===Example 1=== | ||
| − | [[File:5.2.6-fig74.png|right|thumb|300px|Illustration why stratification is most efficient when the ''strata means'' are as different as possible]] | + | [[File:5.2.6-fig74.png|right|thumb|300px|Figure 1: Illustration why stratification is most efficient when the ''strata means'' are as different as possible]] |
| − | Imagine the example population of <math>N=30</math> elements be subdivided into three strata as in | + | Imagine the example population of <math>N=30</math> elements be subdivided into three strata as in figure 1. Here, stratification has been done arbitrarily into three strata of size 14, 8 and 8. |
From this stratified population, we wish to take a sample of <math>n=10</math>, taking <math>n_1=4</math> from the first stratum and <math>n_2=n_3=3</math> from the other two strata. The stratum parametric means and variances are given in Table 1. | From this stratified population, we wish to take a sample of <math>n=10</math>, taking <math>n_1=4</math> from the first stratum and <math>n_2=n_3=3</math> from the other two strata. The stratum parametric means and variances are given in Table 1. | ||
Revision as of 18:33, 16 December 2010
Example 1
Imagine the example population of \(N=30\) elements be subdivided into three strata as in figure 1. Here, stratification has been done arbitrarily into three strata of size 14, 8 and 8.
From this stratified population, we wish to take a sample of \(n=10\), taking \(n_1=4\) from the first stratum and \(n_2=n_3=3\) from the other two strata. The stratum parametric means and variances are given in Table 1.
Table 1: Stratum parameters for the stratified example population.
Stratum \(N_h\,\) \(n_h\,\) \(\mu_h\,\) \(\sigma_h^2\,\) 1 14 4 6.29 3.49 2 8 3 10.13 4.86 3 8 3 5.38 2.48
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