Sampling

1. Starter
True or False
 When a firm is releasing a completely new
product they are likely to use primary research
 20% of the target market would like the
packaging to be silver is an example of qualitative
data
 Government statistics would be an example of
external secondary research
 Secondary research always presents the most up
to date facts and figures
 The bigger the sample the better

2. Sampling

3. Learning Objectives
 Know and understand the purpose of
sampling and analyse the costs and
benefits
 Know the different methods of
sampling and discuss the advantages
and disadvantages of each method
 Give examples of appropriate
sampling methods for given
situations

4. SSaammpplliinngg
 Sampling refers to drawing a
sample (a subset) from a
population (the full set).
 The usual goal in sampling is to
produce a representative
sample

5.  A sample is a set of elements taken
from a larger population.
 A sampling frame is just a list of all
the people that are in the
population.

7. Population
Population – the total number of
people who could be included in a
particular survey.

8. Sampling Methods
 Random Sampling – where everyone in
the population has an equal chance of
being included in the survey
 What is your favourite flavour of ice
cream?
 Do you like marshmallows with your
ice cream?
 What is your favourite brand of ice
cream?

9. Quasi-random 1
 Systematic Sampling – where a
set formula is used (e.g. every
tenth person) to select the people in
the research
EVERYONE
STAND UP!!!

10. Quasi-random 2
 Stratified Sampling – where the
population is divided into smaller
groups, people who are the ones
most likely to be interested in the
product being researched
 Within the selected group a random
or quota sample maybe used to
determine the actual respondents

11. Quasi-random 3
Multi-stage sampling
Involves a number of steps – for example:
First stage, random number of London Boroughs are
chosen.
 Followed by random number of streets.
Then the third stage units will be houses.
 All ultimate units (houses, for instance) selected at
the last step are surveyed.

12. Non-random 1
 Cluster sampling is an example of 'two-stage
sampling' .
 First stage a sample of areas is chosen;
 Second stage a sample of respondents within those
areas is selected.
 Sampling units are groups rather than individuals.
 A sample of such clusters is then selected.
 All units from the selected clusters are studied.

13. Non-random 2
Have you ever been
ambling along your local
High Street, noticed a
Market Researcher with a
clipboard and thought "I
don't mind being asked
some questions - it might
be interesting", only to find
that the researcher looks
 Quota Sampling – attempts to select the
individuals in the survey in relation to the
characteristics of the overall market or population
 Quota sampling is often used in market research.
Interviewers are required to find cases with
particular characteristics. They are given quota of
particular types of people to interview and the
quota are organised so that final sample should
be representative of population.
straight through you?

14. If I asked you to
carry a research
project into music
tastes of students in
College who would
 Convenience Sampling – where
any non-scientific method is used to
help the speed of response and to
lower the cost
WHY?
you ask?

15. Which Method Should Be Chosen?
 Each method has advantages and
disadvantages
 Choice depends on:
 The need for accuracy
 The time available
 The research Budget

16. Sample Size
The larger the sample size, the more
reliable it is likely to be. However,
larger samples incur greater costs:
Expense
Time
Sample size should relate closely to the
size of the specific population.

17. RReelliiaabbiilliittyy ooff ssaammpplliinngg
A 95% confidence level is usually
expected when conducting
research. This means that findings
are likely to be correct 19 times out
of 20.

18. Learning Objectives
 Know and understand the purpose of
sampling and analyse the costs and
benefits
 Know the different methods of
sampling and discuss the advantages
and disadvantages of each method
 Give examples of appropriate
sampling methods for given
situations