Sampling, ethical issues & pilot studies

What is the difference between a population & a sample?

• Population: a group of people who are the focus of the researcher’s interest, from which a smaller sample is drawn

• Sample: a group of people who take part in a research investigation, who are drawn from a target population & is presumed to be representative of that population

What is the definition of a sampling technique?

The method used to select people from the population

What is the definition of random sampling?

Each member of the target population has a mathematically equal chance of being in the experiment’s sample (e.g. computer-based randomiser or picking numbers from a hat)

What are the strengths & limitations of random sampling?

Strengths:

• avoids researcher bias, as the researcher has no influence over who is selected

Limitations:

• difficult & time-consuming → a complete list of the target population may be hard to obtain

• still possible to end up with an unrepresentative sample

• selected participants may refuse to take part → resulting in something more like a volunteer sample

What is the definition of systematic sampling?

Every n^th member of the target population is selected

What are the strengths & limitations of systematic sampling?

Strength:

• avoids researcher bias, as the researcher has no influence over who is selected

Limitations:

• if the list of the target population has not been randomised, there is the possibility of an unrepresentative sample

• a full list of the target population could be difficult if it is large

What is the definition of opportunity sampling?

The researcher asks members of the target population who happen to be willing & available to take part in the study

What are the strengths & limitations of opportunity sampling?

Strength:

• time & cost effective

Limitations:

• sample is unrepresentative of the target population → drawn from a very specific area (low generalisability)

• researcher bias → the researcher has complete control over the selection of participants

What is the definition of volunteer sampling?

Participants select themselves to take part in the research

What are the strengths & limitations of volunteer sampling?

Strengths:

• time & cost effective → requires minimal input from the researcher

• advertisement can reach a large number of potential participants

Limitations:

• volunteer bias → may only attract certain ‘profiles’ of people (low generalisability)

What is the definition of stratified sampling?

The composition of the sample reflects the proportions of people in certain strata within the target population

How is stratified sampling conducted?

1. The researcher identifies the different strata that make up the target population

2. The proportions needed for the sample to be representative are worked out

3. The participants that make up each stratum are selected using random sampling

What are the strengths & limitations of stratified sampling?

Strengths:

• avoids researcher bias, as the researcher has no influence over who is selected

• produces a representative sample (designed to accurately reflect the composition of target population)

Limitations:

• the identified strata cannot reflect all the ways people are different (complete representation of target population is not possible)

• time-consuming to conduct

What are ethical issues?

Arise when a conflict exists between the rights of participants in research studies & the goals of research to produce authentic, valid & worthwhile data

What are all of the ethical issues?

DDRIPP:

• deception

• debrief

• right to withdraw

• informed consent

• protection from psychological harm

• privacy (confidentiality)

What is informed consent?

Making participants aware of the aims of the research, the procedures, their rights & what their data will be used for

What is deception?

Deliberately misleading or withholding information from participants at any stage of the investigation

What is protection from psychological harm?

Participants should not be placed at any more risk than they would be in their daily lives & should be protected from psychological & physical harm

What is privacy & confidentiality?

Participants have the right to control information about themselves & their personal data should be protected

How do researchers obtain informed consent?

• Participants are issued with a consent letter/form, detailing all relevant information that might affect their decision to participate

• For investigations involving children under 16, a signature of parental consent is required

What is presumptive consent?

• Rather than getting consent from the participants themselves, a similar group of people are asked if the study is acceptable

• If this group agree, then the consent of the original participants is ‘presumed’

What is prior general consent?

• Participants give their permission to take part in a number of different studies - including one that will involve deception

• By consenting, participants are effectively consenting to be deceived

What is retrospective consent?

• Participants are asked for their consent (during debriefing) having already taken part in the study

• They may not have been aware of their participation or they may have been subject to deception

How do researchers deal with deception & protection from psychological harm?

At the end of a study, participants are given a full debrief:

• they are made aware of the true aims of the investigation & any details that were withheld from them (e.g. existence of groups or experimental conditions)

• they are told what their data will be used for & must be given the right to withhold data if they wish

• participants may have natural concerns related to their performance within the investigation & so are reassured their behaviour was normal

• in extreme cases, if they have been subject to stress or embarrassment, they are offered counselling

How are debriefs written?

1. Begin with “Thank you for taking part in this study.”

2. Explanation of the aim

3. Information about the method & other conditions

4. Ethical issues, including right to withdraw & reassure privacy

5. Provide the opportunity to be asked questions

How do researchers deal with confidentiality?

• If personal details are used, these must be protected → however, it’s more usual to record no personal details & maintain anonymity

• Researchers usually refer to participants using numbers or initials when writing up the investigation

• During briefing & debriefing, participants are reminded their data will be protected throughout the process

What is the definition of a pilot study?

A small-scale version of an investigation that takes place before the real investigation is conducted:

• the aim is to check that procedures & materials (e.g. questionnaires & interviews) work & to allow the researcher to make changes or modifications if necessary

What is the difference between a single & double blind procedure?

• Single-blind procedure: participants are not told the aim of the research & other details at the beginning of a study

• Double-blind procedure: neither the participants nor the researcher who conducts the study are aware of the aims of the investigation (often a third party conducts the investigation without knowing its main purpose)