Sampling design using the Paddy game

1. Sampling design using the Paddy game (Sessions 15&16)

2. Learning Objectives By the end of these sessions, you will be able to • utilise skills in designing your own sampling scheme to address given objectives • collect data, analyse and present the results appropriately to demonstrate your key findings

3. Paddy demonstration: Aims • To introduce the Paddy game and show how it may be used to select a multi-stage sample • To illustrate, via a small example, how population values can be estimated from sample values Note: a separate handout sets out the aims of the paddy exercise and tasks that you are expected to carry out

4. What is the Paddy Game? • Paddy is a game that has been developed to provide practice on how a sampling design may be developed and the data analysed, once collected • The game uses an example of a survey of rice production • Open the Paddy game on your computer by clicking on the PADDY icon

5. 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.

6. Farmer numbers and their acreages

7. Paddy survey objectives • To estimate the mean yield of rice per hectare and hence the total production of rice in the district • to investigate the use of fertilisers and improved varieties by the farmers • to study the relationship between these factors (fertiliser, variety) and the yield of rice.

8. Crop-cutting survey process • In order to address the objectives, 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 plot covers an area of 1/80th of an acre. • The resources available allow you to visit and collect information from 30 plots. • Yield from each harvested plot is then measured in bushels per acre.

9. 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 • Village as primary sampling unit • Farmer’s field within village as the secondary unit • Plot within field as the final stage unit

10. 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

11. Designing the Sampling scheme

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

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

14. The Sample

15. The Sample in Excel

16. Computing population Estimates

17. Practise playing the Paddy Game • Now practise playing the paddy game yourself using a different sampling scheme to that presented in the previous slide • The aim here is merely to give you practice – it does not matter that the scheme is not suitable for the actual study • You will have 15 minutes for this activity • We will then demonstrate how the computer version can be used to draw a PPS sample

18. Paddy Game with PPS sampling 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

19. Designing the Sampling scheme

20. Designing the Sampling scheme

21. Selecting fields for Village 6

22. Selecting fields for Village 7

23. The Sample

24. Computing population Estimates

25. Now practise drawing a PPS sample. Also read the more detailed handout regarding your tasks for the next two practical sessions…