|
Summary of sampling methods used, outline of sampling technique and example of how the sampling technique relates to real field survey and DSS designs. |
||
| Sampling Method |
Technique |
Example situation in field surveys |
|
|
||
| Simple Random |
Step 1: Assign a random number to each sampling unit |
Cross-sectional surveys within DSS settings |
| Step 2: Sort sampling units by their random number |
||
| Step 3: Select sampling units in ascending order of random numbers until desired sample size is reached |
||
| Probability Proportional to Size |
Step 1: Assign a random number to each sampling unit |
|
| Step 2: Multiply the population of each sampling unit by the random number |
||
| Step 3: Sort sampling units on the number generated in Step 2 |
||
| Step 4: Select sampling units in descending order of number generated in Step 2 until desired sample size is reached |
||
| Proportional Stratified Sampling |
Step 1: Determine the proportion of sampling units needed in each strata |
Cross-sectional surveys within DSS settings or establishing a DSS |
| Step 2: Assign a random number to each sampling unit |
||
| Step 3: Select sampling units from each strata using simple random methods until the desired sample size and ratio between strata is obtained |
||
| Multi-stage Sampling (Stage 1 random; Stage 2 random) |
Step 1: Randomly select geographical area for sampling |
Establishing a DSS |
| Step 2: Assign a random number to each sampling unit in the selected area |
||
| Step 3: Sort sampling units by their random number |
||
| Step 4: Select sampling units in ascending order of random number until desired sample size is reached |
||
| Multi-stage Sampling (Stage 1 random; Stage 2 PPS) |
Step 1: Randomly select geographical area |
|
| Step 2: Assign a random number to each sampling unit in the selected area |
||
| Step 3: Multiply the population of each sampling unit by the random number |
||
| Step 4: Sort sampling units on the number generated in Step 3 |
||
| Step 5: Select sampling units in descending order of number generated in Step 3 until desired sample size is reached |
||
| Geographically Dispersed (Stage 1 random; Stage 2 random; Stage 3 random) |
Step 1: Randomly select two geographical areas |
Multi-centre study |
| Step 2: Assign a random number to each sampling unit in each of the selected areas |
||
| Step 3: Sort sampling units by their random number |
||
| Step 4: Select sampling units in ascending order of random number until 50% of the desired sample is selected from each geographical area |
||
| Geographically Dispersed (Stage 1 random; Stage 2 random; Stage 3 PPS) |
Step 1: Randomly select two geographical areas |
|
| Step 2: Assign a random number to each sampling unit in each of the selected areas |
||
| Step 3: Multiply the population of each sampling unit by the random number |
||
| Step 4: Sort sampling units on the number generated in Step 3 |
||
| Step 5: Select sampling units in descending order of number generated in Step 3 until 50% of the sample is selected from each geographical area |
||
Fottrell and Byass Population Health Metrics 2008 6:2 doi:10.1186/1478-7954-6-2 |
||