AP Statistics : How to do a random selection for a survey
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Example Question #2 : How To Conduct A Sample Survey
Which of the following is the best way to ensure a sample is representative and unbiased?
None of the other answers
Take a convenience sample
Take a random sample
Take a census
Take a voluntary response sample
Take a random sample
Taking a random sample is the only data-collecting method that ensures that every set of individuals has an equal chance of being selected for the sample and does not introduce any significant bias. Taking either a voluntary response sample or a convenience sample does not ensure these important aspects, as there is some unwanted selectivity involved in the data being collected. Taking a census is inferior to taking a sample of any sort, as it is both costly and time-consuming.
Example Question #1 : How To Do A Random Selection For A Survey
John would like to find out what percentage of residents in his neighborhood enjoy shopping. Which of the following is the best method to randomly select participants to take John's survey?
There is no effective way to randomly select participants to be surveyed
John can sit at the park in his neighborhood and survey every individual that passes by to determine if they enjoy shopping
John can go to his local mall and survey individuals at random to determine if they enjoy shopping
John can number residents his neighborhood and randomly select residents to survey using a random number generator
John can go to his local grocery store and survey individuals at random to determine if they enjoy shopping
John can number residents his neighborhood and randomly select residents to survey using a random number generator
The best answer is the choice that reduces the amount of bias in the selection of survey participants. Surveying local residents at a grocery store, neighborhood park, or shopping mall would introduce selection bias into the survey since every member of the target population does not have an equal chance of being selected. Using the random number generator, every single person in the neighborhood has an equal chance of being selected to take the survey.
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