Methods of Producing Data

1. Methods of Producing Data • Sampling: drawing subsets from the population • Experimentation: impose a change and measure the result • Simulation: numerical facsimile of real-world phenomena • Census: using measurements from entire population • Survey: asking questions

2. Simple Random Sample of n measurements: • every sample of size n has equal chance of being selected • every item in the population has equal chance of being included

3. Not random sampling: asking for volunteers to respond to a survey choosing the first five customers in a store

4. Random sampling: • drawing names “from a hat” • using a random number table to select sample • using a random number generator

5. Simulation • Provides arithmetic imitation of “real” phenomenon • Random number table may be used

6. Sampling with replacement The same number may be selected for a sample more than one time.

7. Other sampling techniques • Stratified Sampling • Systematic Sampling • Cluster Sampling • Convenience Sampling

8. Stratified Sampling Population is divided into groups (“strata”) Random samples are drawn from each group

9. Systematic Sampling Population is arranged in sequential order. Select a random starting point. Select every “kth” item.

10. Cluster Sampling Population is divided into sections Some sections are randomly selected Every item in selected sections is included in sample

11. Convenience Sampling Use whatever data is readily available. Risk severe bias.

12. Which sampling technique is described? College students are waiting in line for registration. Every eighth person in line is surveyed. Systematic sampling

13. Which sampling technique is described? College students are waiting in line for registration. Students are asked to volunteer to respond to a survey. Convenience sampling

14. Which sampling technique is described? In a large high school, students from every homeroom are randomly selected to participate in a survey Stratified sampling

15. Which sampling technique is described? An accountant uses a random number generator to select ten accounts for audit. Simple random sampling

16. Which sampling technique is described? To determine students’ opinions of a new registration method, a college randomly selects five majors. All students in the selected majors are surveyed. Cluster sampling