1. Sampling
Learning Objectives
• ALL – to know different
sampling methods
• MOST – reflect on advantages
and disadvantages of sampling
• SOME – consider the effects of
bias

2. What I KNOW What I WOULD What I have The RANK order
about sampling LIKE to know LEARNT about of what I have
about sampling sampling learnt today is
(the most
important)
Complete the first two
columns of your KWL
grid.
Learning Objectives
• ALL – to know different sampling methods
• MOST – reflect on advantages and disadvantages of
sampling
• SOME – consider the effects of bias

3. 1. it is quicker than measuring
every item
2. it is therefore much cheaper
3. often it is impossible to
measure everything The size of the
sample will usually be
4. it is unnecessary to measure
dictated by the time
everything
and resources
5. it is sometimes impossible to available. BUT the
gain access to everything larger the sample
Learning Objectives the more likely it is
• ALL – to know different sampling methods to find a true
• MOST – reflect on advantages and disadvantages of picture of the data
sampling you are sampling.
• SOME – consider the effects of bias

4. You will be conducting a mini investigation to
practise sampling. You will be using smarties to
demonstrate the different sampling techniques.
Do not eat your smarties as you can’t carry out
the investigation without them – make it to the
end and then you can eat them!!
Stretch and challenge – for each type of sampling
method you must attempt to write up your own
definition of this technique.
Learning Objectives
• ALL – to know different sampling methods
• MOST – reflect on advantages and disadvantages of
sampling
• SOME – consider the effects of bias

5. Random sampling means that
members of a 'population' have
equal chances of being selected.
To carry out this type of sampling,
Lay out your smarties in a
you will need to use a table of row. Assign each smartie a
random numbers. Random number from 1- 20(we will
numbers can also be generated deal with a population of
20 smarties).
using a calculator or computer.
A random number
Learning Objectives calculator will generate
numbers to identify which
• ALL – to know different sampling methods
smarties will be part of the
• MOST – reflect on advantages and disadvantages of random sample.
sampling
• SOME – consider the effects of bias

6. Advantages Disadvantages
No human bias If the sample size is small
involved in the we may by bad luck
selection obtain an
process. unrepresentative result
Learning Objectives
• ALL – to know different sampling methods
• MOST – reflect on advantages and disadvantages of
sampling
• SOME – consider the effects of bias

7. What I KNOW What I WOULD What I have The RANK order
about sampling LIKE to know LEARNT about of what I have
about sampling sampling learnt today is
(the most
important)
Add 3
things you
have learnt
to your
table
Learning Objectives
• ALL – to know different sampling methods
• MOST – reflect on advantages and disadvantages of
sampling
• SOME – consider the effects of bias

8. Sampling data at equal distances
apart e.g. every fifty meters or
every 10th person.
Lay out your smarties
in a row. Assign each
smartie a number
from 1- 20(we will
deal with a population
of 20 smarties).
Learning Objectives
Take every 5th smartie
• ALL – to know different sampling methods
– this will be your
• MOST – reflect on advantages and disadvantages of
sampling
systematic sample.
• SOME – consider the effects of bias

9. Advantages Disadvantages
Ensures If the sample size is small
complete we may by bad luck
coverage of the obtain an
sample area. unrepresentative result
Learning Objectives
• ALL – to know different sampling methods
• MOST – reflect on advantages and disadvantages of
sampling
• SOME – consider the effects of bias

10. 'Strata' means All the sweets are smarties but each
'layer'. A stratified smartie has a different colour and the
sample is made up colour represents a subjection of the
of different 'layers' whole population. Select out all the red
of the population, smarties these are the stratified sample.
for example,
selecting samples
from different age
groups.
Learning Objectives
• ALL – to know different sampling methods
• MOST – reflect on advantages and disadvantages of
sampling
• SOME – consider the effects of bias

11. Advantages Disadvantages
Helps to reduce bias Sometimes difficult
because all sub groups to identify a sub
of the population are group or strata
included in the sample
Learning Objectives
• ALL – to know different sampling methods
• MOST – reflect on advantages and disadvantages of
sampling
• SOME – consider the effects of bias

12. What I KNOW What I WOULD What I have The RANK order
about sampling LIKE to know LEARNT about of what I have
about sampling sampling learnt today is
(the most
important)
Add 3
things you
have learnt
to your
table
Learning Objectives
• ALL – to know different sampling methods
• MOST – reflect on advantages and disadvantages of
sampling
• SOME – consider the effects of bias

13. Q. Collecting sediment samples every 10m on a beach
A. Systematic
Q. In a beach questionnaire ensuring that participants both
young and old are asked.
A. Stratified
Q. Numbers are generated using a computer and these numbers
are used as grid reference co ordinates for the site of study
A. Random
Q. In a sand dune investigation choosing a sample where there is
a break of slope rather than at equally spaced intervals
A. Stratified
Learning Objectives
• ALL – to know different sampling methods
• MOST – reflect on advantages and disadvantages of
sampling
• SOME – consider the effects of bias

14. Select out your favourite colour
smarties and eat them – this
would be a bias sample! Why?
Learning Objectives
• ALL – to know different sampling methods
• MOST – reflect on advantages and disadvantages of
sampling
• SOME – consider the effects of bias

15. What I KNOW What I WOULD What I have The RANK order
about sampling LIKE to know LEARNT about of what I have
about sampling sampling learnt today is
(the most
important)
Add 2-4 things you have
learnt this lesson and
decide which is the most
important thing you have
Learning Objectives learnt or rank order
• ALL – to know different sampling methods everything you have
learnt from top to
• MOST – reflect on advantages and disadvantages of
bottom.
sampling
• SOME – consider the effects of bias