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Multistage Sampling

Multistage Sampling. Module 3 Session 9. Session Objectives. To introduce Multistage sampling To help participants appreciate when to apply multi-stage sampling. Multi-Stage Sampling Design. Most commonly used sampling design in practice

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Multistage Sampling

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  1. Multistage Sampling Module 3 Session 9

  2. Session Objectives • To introduce Multistage sampling • To help participants appreciate when to apply multi-stage sampling

  3. Multi-Stage Sampling Design • Most commonly used sampling design in practice • Involves more than one stage of sampling and/or a combination of two or more sampling designs

  4. Why apply multi-stage sampling • Structure of the population • Size of population (large) • Fund available for the survey

  5. Examples of multi-stage sampling • A Systematic sample of households within Enumeration Areas (EAs) within Districts • Districts – Strata – 1st Stage • EAs- Clusters- 2nd Stage • Households -3rd Stage • Within each District take a sample of EAs • Within each EAs, take a sample of h’holds • Within each household, sample 2 individuals

  6. Cont’d • Determine from students at a university their opinion of the university. • Stratify students according to their Faculty (Science, etc.) (strata 1st ) • Take simple random sample of courses in each of these Faculties (clusters 2nd ) • From each course take a random sample of students.

  7. Sampling and Analysis issues using the Paddy Game Module 3 Session 9(b)

  8. To introduce basic sampling concepts using the Paddy game To demonstrate how to select a sample from a population To demonstrate how population values can be estimated from samples Session Objectives

  9. Paddy is a game that has been developed to demonstrate how to design and analyse survey data The game uses an example of a survey of rice production Open the paddy game on your computer by clicking on the PADDY icon. What is Paddy?

  10. Background Information • In a small district there are: • 10 villages • With a total of 160 farmers • Each with one field in which to grow rice • A census has been undertaken and the acreage cultivated by each farmer is known.

  11. Number of Farmers & Acreage - by Village

  12. Aim of the Survey • The main aim of the survey is to estimate the mean yield of rice per hectare and hence the total production of rice in the district • In order to do this you will carry out a crop cutting survey. This is a survey where you visit fields, harvest the crop from one or more plots and measure the yield • A further objective is to investigate the use of fertiliser and varieties by the farmers

  13. Resources • The resources available allow you to visit and collect information from 30 plots. • A plot covers an area of 1/80th of an acre. • Yield from each plot harvested is then measured in bushels per acre.

  14. Resources • Transport costs allow your survey team to visit a maximum of 5 villages, although you might decide to visit less than 5. • These costs dictate that the survey should use a multistage sampling design

  15. Resources • The game gives you the possibility of three levels: • Villages • Farmers within Village • Plots within farmers.

  16. Pilot Run • We begin with a pilot run to give you familiarity with the Paddy game • The Paddy game has been installed on your computers • The sampling scheme suggested is the following: • Select 2 villages using simple random sampling • From each village select 3 fields, again with simple random sampling • From each field, select 1 plot at random for harvesting

  17. Designing the Sampling scheme

  18. Designing the Sampling Scheme- Selecting fields in village 6 -

  19. Designing the Sampling Scheme- Selecting fields in village 7 -

  20. The Sample

  21. Probability Proportional to Size (PPS) Sampling using the Paddy Game Module 3 Session 9(c)

  22. Session Objectives • To demonstrate how to select a sample from a population using PPS • To demonstrate how population values can be estimated from samples

  23. Pilot Run • Suppose the sampling scheme suggested is the following: • Select 2 villages using PPS sampling where the sample depends on the number of farmers in the village • From each village select 3 fields, with simple random sampling • From each field, select 1 plot at random for harvesting

  24. Designing the Sampling scheme

  25. Designing the Sampling scheme

  26. Selecting fields for Village 6

  27. Selecting fields for Village 7

  28. The Sample

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