139
Complex Samples Sampling Wizard
inclusion probability matrices are 4×4 for these strata, and the Joint_Prob_5_ column is left empty for these rows. Similarly, strata 3 and 5 have 3×3 joint inclusion probability matrices, and stratum 4 has a 5×5 joint inclusion probability matrix.
The need for a joint probabilities file is seen by perusing the values of the joint inclusion probability matrices. When the sampling method is not a PPS WOR method, the selection of a PSU is independent of the selection of another PSU, and their joint inclusion probability is simply the product of their inclusion probabilities. In contrast, the joint inclusion probability for Townships 9 and 10 of County 1 is approximately 0.11 (see the first case of Joint_Prob_3_ or the third case of Joint_Prob_1_), or less than the product of their individual inclusion probabilities (the product of the first case of Joint_Prob_1_ and the third case of Joint_Prob_3_ is 0.31×0.44=0.1364).
The pollsters will now conduct interviews for the selected sample. Once the results are available, you can process the sample with Complex Samples analysis procedures, using the sampling plan poll.csplan to provide the sampling specifications and poll_jointprob.sav to provide the needed joint inclusion probabilities.
Related Procedures
The Complex Samples Sampling Wizard procedure is a useful tool for creating a sampling plan file and drawing a sample.
To ready a sample for analysis when you do not have access to the sampling plan file, use the Analysis Preparation Wizard.
