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Surveys/Experiments Observation. 2 sample project instructions. Avoid Bias Results. What makes a sample bad? Voluntary Response Sample Biased towards those with strong opinions. Avoid Bias Results. What makes a sample bad? Voluntary Response Sample
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Surveys/ExperimentsObservation 2 sample project instructions
Avoid Bias Results • What makes a sample bad? • Voluntary Response Sample • Biased towards those with strong opinions
Avoid Bias Results • What makes a sample bad? • Voluntary Response Sample • Biased towards those with strong opinions • What would you be more likely to respond to: • Raise the license age to 25 and revoke current licenses from younger drivers
Avoid Bias Results • What makes a sample bad? • Voluntary Response Sample • Biased towards those with strong opinions • What would you be more likely to respond to: • Raise the license age to 25 and revoke current licenses from younger drivers • Change school dress code policy
Avoid Bias Results • What makes a sample bad? • Convenience Sample
Avoid Bias Results • What makes a sample bad? • Convenience Sample • Heights of the first person in each row
How can I obtain non biased results? • Good sampling methods • Simple random sample • Lottery drawing • Systematic • Every 10th person in an alphabetical list • Cluster • Survey 2 freshman HR and 2 senior HR
Example • Sample Letter to HR teacher: Dear Senior Homeroom Teacher, Our Probability and Statistics class is collecting research for a statistical study. It is important that all students fill out the attached survey so that I can obtain accurate results. Please encourage your students to complete the survey honestly and accurately. Thank you for your time. I will be stopping by during 3rd period on Friday to pick up the completed surveys. Sincerely,
Probability and Statistics Survey Dear Student, Our Probability and Statistics class is collecting research for a statistical study. Please complete the following questions honestly and accurately. All responses are anonymous. • How many times do you eat in a day? _____ • Circle one: I am a male / female