Unit 3 Flashcards
Example: Does regular exercise decrease the risk of cancer? A research finds 200 woman over 50 who exercise regularly, pairs each with a woman who has a similar medical history but does not exercise, then follows the subjects for 10 years to see which group develops more cancer.
Prospective Study
Example: Place an announcement in the newspaper asking people to call their council representatives to register their opinions. Council members will tally the calls they receive.
Voluntary Response Bias
Have each council member survey 50 friends, neighbors, or co-workers.
Convenience Bias
Have the Board of Elections assign each voter a number, then select 400 of them using a random number table.
Simple Random Sample (SRS)
Go to a downtown street corner, a grocery store, and a shopping mall; interview 100 typical shoppers at each location.
Judgement Bias
Randomly pick 50 voters from each election district.
Stratified Sample
Call every 500th person in the phone book.
Systematic
Randomly pick several city blocks, then randomly pick 10 residents from each block.
Multistage
Randomly select several city blocks; interview all the adults living on each block.
Cluster
The primary purpose is to reduce variation
Blocking
Example: If a statistics teacher decides that instead of randomly selecting students to survey on how they feel about the course she just asks students to volunteer for the survey.
Volunteer Response Bias
If a statistics teacher decides that instead of randomly selecting students to survey on how they feel about the course she just gives the survey during class one day.
Convenience Bias
Primary purpose is to reduce bias
Blinding
A study based on data in which no manipulation of factors has been employed
Observational Study
Definition: An observational study in which subjects are selected and then their previous conditions or behaviors are determined
Retrospective Study
