Class #9: More about sampling

1. Economic sample – provides a reasonably accurate estimate of the population at reasonable effort and cost.

2. Things that influence the accuracy of a sample:
-Sample size (the larger, the better)
-Population size (the larger population, the larger sample needed)
-Variance of the data (larger sample size will capture the extreme scores better)

3. Random Samples (Examples):

• Simple Random Sampling: pulling raffle tickets out of a box
• Systematic Random Sampling: randomize the students in our class first, then make every 5th person take an extra exam 🙂
• Stratified Random Sampling:

• Proportionate Random Sampling:

4. Cluster sampling & Multistage clustering

5. Problem of nonresponse: more error.
Solutions: Follow-up with respondents; Incentivize; determine if respondents and nonrespondents differ systematically.

6. Nonprobability Sample

• Convenience Sampling: College students enrolled in Intro to PSY
• Quota Sampling: making sure half of the sample agree with the topic, half disagree
• Purposive Sampling: choosing those who the researcher thinks are most typical of the population

7. Power – the ability of a research design to detect any effects of the variables being studied that exist in the data.
The larger the sample, the higher power.