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Sampling Bias

Sampling Bias. Sampling Bias occurs when the technique used tends to favor one part of the population. Nonresponse Bias occurs when individuals choose not to respond.

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Sampling Bias

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  1. Sampling Bias • Sampling Bias occurs when the technique used tends to favor one part of the population. • Nonresponse Bias occurs when individuals choose not to respond. • Response Bias occurs when only the strongly committed respond. You author says when the response does not reflect the individuals true feeling.

  2. Interviewer Error occurs when the interviewer fails to record the response correctly. Or the interviewer elicits a specific response from the individual. • Nonsampling errors occur when the survey or experiment are done incorrectly. Ex: If any form of bias occurs. Mistakes in recording data

  3. Wording Bias A PHRASE OF THE QUESTION THAT DRAWS A SPECIFIC RESPONSE. Should stem cell research be funded by the government? Should stem cell research be funded using tax dollars? Should the government use our tax dollars to fund stem cell research? Should the government give tax dollars away to private industry to help in stem cell research? Should the government help cure diseases by funding stem cell research? Since stem cell research will help cure major diseases the government needs to support this important research. Do your agree or disagree?

  4. ORDERING OF QUESTIONS The order the questions are give will change the response. Do you think we should prohibit smokers from smoking in open public places? Do you think we should force non-smokers to breath cigarette smoke from nearby smokers ? Do you think we should force non-smokers to breath cigarette smoke from nearby smokers ? Do you think we should prohibit smokers from smoking in open public places?

  5. Design of Experiment 1. Identify a problem 2. Determine the factors: Explanatory variables (Control variable) or “factors” Response variable is the variable of interest Determine the level of the factors Control: fix the values so they do not affect the outcome Manipulate the variables you want to measure for response Randomize to minimize effect of uncontrolled factors • Repeat the process by treating several subjects repetition occurs. • Measure affect on response variable from explanatory • Collect data • Make Inference – draw a conclusion

  6. Types of Experiments MATCHED PAIRS: experimental units are matched together by some relation. Usually a before and after. Testing the affect of octane rating in gasoline to miles per gallon. RANDOMIZE BLOCKING: units are divided into Homogeneous (similar) groups called blocks Discuss fish food problem.

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