Sampling Methods Lecture

Introduction

• Clarification: Focus is on sampling methods, not experimental design.
• Sampling Methods: How participants are recruited for research.
• Importance: Understanding participant recruitment is essential for research.

Key Concepts

Populations

• General Population: Everyone in the world.
• Target Population: A subset of the general population aimed at in research, e.g., students at Barn Pedro.

Representative Sample

• Purpose: To generalize results from the sample to the target population.
• Requirements: Representative in size, ethnicity, gender, religious beliefs, etc.

Sampling Methods

1. Opportunity Sampling (Convenient Sampling)

• Description: Approaching people directly to participate.
• Pros:
  • Easy and quick to perform.
• Cons:
  • Labor-intensive with high rejection rates.
  • Highly biased; not truly random.
  • Researchers may unconsciously select supportive participants.

2. Volunteer Sampling (Self-Selection)

• Description: Participants come forward in response to an advertisement.
• Pros:
  • Less time-consuming; participants self-select.
  • Low attrition rate; participants are more willing.
• Cons:
  • Attracts a specific type of participant (volunteer personality).
  • May not represent the entire target population; lowers validity.

3. Random Sampling

• Description: Use of the "hat method" to ensure every individual has an equal chance of selection.
• Pros:
  • No researcher bias.
  • Participants are randomly selected.
• Cons:
  • Time-consuming as recruitment continues until consent is obtained.

4. Systematic Sampling

• Description: Selection of every nth individual from a list.
• Pros:
  • No researcher bias.
  • Representative sample.
• Cons:
  • Similar to random sampling but follows a systematic pattern.

5. Stratified Sampling

• Description: Ensures sample reflects the proportions of subgroups in the target population.
• Example: If population is 70% female, sample must reflect this proportion.
• Pros:
  • Accurately reflects the target population.
• Cons:
  • Requires knowledge of population proportions.

Common Exam Questions

• Key Idea: Sampling method identification is a common exam topic.
• Important: Familiarize with each method and its characteristics.

Conclusion

• Next Steps: Review exam examples and focus on experimental designs in upcoming lectures.