IB Psychology Topic 2.4 Research Methodology Revision…

2.4.4 Sampling Techniques

Sampling Techniques: How Researchers Choose Participants

Imagine you're conducting a study on stress levels among high school students.
You can't possibly survey every student in the world, so you need a sample, a smaller group that represents the larger population.
The way you select this sample can significantly impact the results of your study.

Self-Selected Sampling

In self-selected sampling, participants volunteer to be part of the study.
This method is often used in online surveys or studies advertised through posters or social media.

Example

A researcher posts a survey link on a school's website, inviting students to participate in a study on exam stress.
The students who choose to participate form a self-selected sample.

Strengths and Limitations

Note

Strengths

Easy to recruit participants.
Participants are often motivated and engaged.

Note

Limitations

Volunteer bias: Participants may differ from the general population (e.g., more motivated or extroverted).
Not always representative, limiting generalizability.

Opportunity Sampling

Opportunity sampling involves selecting participants who are readily available and willing to participate.
This method is common in classroom studies or research conducted in public places.

Example

A researcher studying memory asks students in a nearby classroom to participate during their free period.

Strengths and Limitations

Note

Strengths

Quick and easy to implement.
Cost-effective.

Note

Limitations

High risk of sampling bias.
May not be representative of the larger population.

Case study

Milgram (1963)

Aim: To study obedience to authority.

Method: Participants believed they were administering electric shocks to a learner (confederate) under the instruction of an authority figure.

Results: 65% of participants administered the highest shock level.

Conclusion: People are likely to follow authority figures, even against their morals.

Relevance: Milgram used opportunity sampling, recruiting participants through newspaper ads and local flyers, which may have attracted individuals more interested in authority or obedience studies.

Stratified Sampling

A sampling technique where the population is divided into subgroups called strata, and participants are randomly selected from each subgroup in proportion to their representation in the population.

Example

A researcher studying workplace stress ensures the sample includes 50% women and 50% men, reflecting the gender distribution in the target population.

Strengths and Limitations

Note

Strengths

Increases representativeness.
Reduces sampling bias by ensuring all subgroups are included.

Note

Limitations

Time-consuming and complex to organize.
Requires detailed knowledge of the population's characteristics.

Random Sampling

A sampling technique where every member of the population has an equal chance of being selected.

Example

A researcher assigns numbers to all students in a school and uses a random number generator to select participants.

Strengths and Limitations

Note

Strengths

Minimizes sampling bias.
Results are more likely to be generalizable.

Note

Limitations

Can be impractical for large or hard-to-reach populations.
May still result in unrepresentative samples by chance.

Snowball Sampling

A sampling technique where existing participants recruit future participants from among their acquaintances.

Note

Snowball sampling is often used in qualitative research or when studying hard-to-reach populations.

Example

A researcher studying the experiences of undocumented immigrants asks participants to refer others they know.

Strengths and Limitations

Note

Strengths

Effective for accessing hidden or stigmatized groups.
Builds trust through participant referrals.

Note

Limitations

High risk of sampling bias, as participants are likely to recruit similar individuals.
Limited generalizability.

Active recall

How do different sampling techniques impact the generalizability of research findings?
What are the ethical considerations associated with each sampling method?
How might sampling bias influence the results of a study on mental health in adolescents?

2.4E Sampling techniques: who ends up in the study and why it matters

2.4E Sampling techniques: who ends up in the study and why it matters

Subtopics and learning objectives

2.4.4 Sampling Techniques

Sampling Techniques: How Researchers Choose Participants

Self-Selected Sampling

Strengths and Limitations

Opportunity Sampling

Strengths and Limitations

Stratified Sampling

Strengths and Limitations

Random Sampling

Strengths and Limitations

Snowball Sampling

Strengths and Limitations

Sampling Techniques: How Researchers Choose Participants

Self-Selected Sampling

Strengths and Limitations

Opportunity Sampling

Strengths and Limitations

Stratified Sampling

Strengths and Limitations

Random Sampling

Strengths and Limitations

Snowball Sampling

Strengths and Limitations

1. Concepts

2. Content

3. Contexts

4. Extensions (HL only)

1. Concepts

2. Content

3. Contexts

4. Extensions (HL only)

2.4E Sampling techniques: who ends up in the study and why it matters

2.4E Sampling techniques: who ends up in the study and why it matters

Subtopics and learning objectives

2.4.4 Sampling Techniques

2.4.4 Sampling Techniques

Sampling Techniques: How Researchers Choose Participants

Self-Selected Sampling

Strengths and Limitations

Opportunity Sampling

Strengths and Limitations

Stratified Sampling

Strengths and Limitations

Random Sampling

Strengths and Limitations

Snowball Sampling

Strengths and Limitations

Sampling Techniques: How Researchers Choose Participants

Self-Selected Sampling

Strengths and Limitations

Opportunity Sampling

Strengths and Limitations

Stratified Sampling

Strengths and Limitations

Random Sampling

Strengths and Limitations

Snowball Sampling

Strengths and Limitations