Chapter 3 lecture

Chapter 3 lecture - Chapter 3 and Section 2.6 Lecture...

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Chapter 3 and Section 2.6 Lecture: Experimental and sampling design, ethics, causation Ellen Gundlach STAT 301 Course Coordinator Purdue University
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Population vs. Sample Population Sample (parameter) (statistic)
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Design of a sample Voluntary Response Sample NOT RANDOM, NOT THE BEST sometimes the only ethical choice for experiments using people Random Selection of a Sample MUCH BETTER
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Types of random samples Simple random sample (SRS) Stratified random sample Multistage sample Capture-Recapture sample
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Capture-Recapture Sample J.B. Landers from www.causeweb.org
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How to take a Simple Random Sample (SRS) Random number table Table B in Appendix of your textbook Course website, “Additional resources” SPSS
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Taking a Simple Random Sample (SRS) Example A club at Hogwarts needs to take a random sample of 4 members to be representatives at a Worldwide Wizarding Workshop. Each member should have an equal chance of being selected. Here are the 12 club members: Harry Luna George McGonigal Hermione Neville Fred Dumbledore Ron Sirius Ginny Lupin
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Taking a Simple Random Sample (SRS) Example Here’s what part of Table B looks like (starting at line 130): 69051 64817 87174 09517 84534 06489 87201 97245 05007 16632 81194 14873 04197 85576 45195 96565 68732 55259 84292 08796 43165 93739 31685 97150 45740 41807 65561 33302 07051 93623 18132 09547
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Taking a Simple Random Sample (SRS) Example Since we have 12 club members, we need to assign each a two-digit code number. 01 Harry 04 Luna 07 George 10 McGonigal 02 Hermione 05 Neville 08 Fred 11 Dumbledore 03 Ron 06 Sirius 09 Ginny 12 Lupin
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Taking a Simple Random Sample (SRS) Example 69 05 1 6 4817 8717 4 095 17 84 534 0 6489 8720 1 972 45 05 007 1 6632 8119 4 148 73 04 197 85576 45195 96565 68732 55259 84292 08796 43165 93739 31685 97150 45740 41807 65561 33302 07051 93623 18132 09547
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Taking a Simple Random Sample (SRS) Example 69 05 1 6 4817 8717 4 095 17 84 534 0 6489 8720 1 972 45 05 007 1 6632 8119 4 148 73 04 197 85576 45195 96565 68732 55259 84292 08796 43165 93739 31685 97150 45740 418 07 65561 333 02 07051 93623 18132 09547 Our 4 club members are going to the Worldwide Wizarding Workshop are: Neville (05) Luna (04) George (07) Hermione (02)
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Using SPSS to take a SRS Harry 1 Hermione 0 Ron 0 Luna 1 Neville 1 Sirius 0 George 0 Fred 0 Ginny 1 McGonigal 0 Dumbledore 0 Lupin 0
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Problems with Sampling Undercoverage Nonresponse Response Bias
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Response bias
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Undercoverage/response bias
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Ways to get data Observational study Stand back and watch Survey Experiment deliberately imposes some treatment Anecdotal Evidence NOT good science!
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Survey Designs To judge the quality of a survey, check: Wording of exact question posed Amount of nonresponse Sampling design Date of the survey
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Survey Questions, Part 1 http://www.stat.purdue.edu/~gundlach/Lectures%20STAT%20301/Parks&Rec1.wmv
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Survey Questions, Part 2 http://www.stat.purdue.edu/~gundlach/Lectures%20STAT%20301/Parks&Rec2.wmv
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Why are experiments better than observational studies?
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  • Spring '08
  • Staff
  • Randomness, Simple random sample, Harry Hermione Ron Luna Neville Sirius George Fred Ginny McGonigal Dumbledore Lupin

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