1 / 10

Sections 1.4: Other Effective Sampling Methods 1.5: Bias in Sampling

Sections 1.4: Other Effective Sampling Methods 1.5: Bias in Sampling 1.6: The Design of Experiments General goals Collect data effectively Avoid bad data Clever ways to best answer the question at hand.

lars
Télécharger la présentation

Sections 1.4: Other Effective Sampling Methods 1.5: Bias in Sampling

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Sections • 1.4: Other Effective Sampling Methods • 1.5: Bias in Sampling • 1.6: The Design of Experiments • General goals • Collect data effectively • Avoid bad data • Clever ways to best answer the question at hand

  2. A local news radio station invites morning listeners to respond to a opinion question about a current news issue. The listeners are given one of two phone numbers: one for if you “agree” and another if you “disagree”. This is an example of: • Stratified sampling • Systematic sampling • Cluster sampling • Convenience sampling

  3. Suppose I wanted to find out HSU students’ opinion about their knowledge of the Jack Pass for the local bus system. Using student records, I randomly selected 20 first year students, 20 second year students, 20 third year students, and 20 student who were fourth or greater year students. This is an example of: • Stratified sampling • Systematic sampling • Cluster sampling • Convenience sampling

  4. What would a possible cluster sampling design look like for surveying students about their bus use?

  5. In attempt to predict the 1936 presidential election, The Literary Digest surveyed a sample collected from its readers and from a registry of car owners and telephone users. The survey predicted the Republican candidate Alf Landon would easily beat Democrat president Franklin Roosevelt. (source: Wikipedia). You’ve likely never had heard of Alf Landon, so obviously the survey was off in its prediction. What went wrong?

  6. Where did it go wrong? • Nonresponse bias: Only 2.3 million of the 10 million readers responded to survey • Sampling bias: The ownership of cars and phones excluded many poor and/or rural people.

  7. Suppose a public health survey is being designed to learn about people’s sexual behavior and their perceived risk for acquiring and/or transmitting STDs. Question: What type of bias(es) should researchers be concerned about? • Sampling & Nonresponse • Nonresponse & Response • Sampling & Response • Sampling & Nonresponse & Response

  8. To test the effect of caffeine and blood pressure (bp), 100 volunteers were given a placebo pill one day and then had their bp measured. Likewise, on an adjacent day each person was given a caffeine pill and their bp measured. The order of placebo or caffeine was randomly set.

  9. This is an example of: • Matched-pairs design • Multistage sampling • Double blind study • Systematic sampling

  10. Some big ideas about designing a study: • Determine the question. • Determine the parameter of interest. • Determine the population. • Be aware of and avoid bias • Control for what you can (blocking, matched-pairs, etc) and randomize the rest. • Think of confounding variables, especially in observational studies. • Play “Devil’s advocate” and then redesign.

More Related