Sampling 2014

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

Sampling

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

SamplingSampling

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

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.

Population

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

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?

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!!!

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

Quasi-random 3

Multi-stage samplingInvolves 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.

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.

Non-random 2

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.

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

straight through you?

Convenience Sampling – where any non-scientific method is used to help the speed of response and to lower the cost

If I asked you to carry a research

project into music tastes of students in College who would

you ask?

WHY?

Which Method Should Be Chosen?

Each method has advantages and disadvantages

Choice depends on: The need for accuracy The time available The research Budget

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.

Reliability of samplingReliability of sampling

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

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