Multistage
Sampling
Module 3
Session 9
1
Session Objectives

To introduce Multistage sampling

To help participants appreciate when to apply
multi-stage sampling
2
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
3
Why apply multi-stage
sampling

Structure of the population

Size of population (large)

Fund available for the survey
4
Examples of multi-stage
sampling
1.
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
5
Cont’d
2.
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.
6
Sampling and
Analysis issues using
the Paddy Game
Module 3
Session 9(b)
7
Session Objectives



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
8
What is Paddy?



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.
9
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.
10
Number of Farmers & Acreage
- by Village
11
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
12
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.
13
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
14
Resources

The game gives you the possibility of three
levels:



Villages
Farmers within Village
Plots within farmers.
15
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
16
Designing the Sampling scheme
17
Designing the Sampling Scheme
- Selecting fields in village 6 -
18
Designing the Sampling Scheme
- Selecting fields in village 7 -
19
The Sample
20
Probability Proportional
to Size (PPS) Sampling
using the Paddy Game
Module 3
Session 9(c)
21
Session Objectives

To demonstrate how to select a sample
from a population using PPS

To demonstrate how population values
can be estimated from samples
22
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
23
Designing the Sampling
scheme
24
Designing the Sampling
scheme
25
Selecting fields for Village 6
26
Selecting fields for Village 7
27
The
Sample
28