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Single Factor Research

Single Factor Research. If I want to test the efficacy of a new drug on blood pressure then I have some choices of design…. Two independent samples Control vs drug groups (random assignment) Comparison is independent t- test Or Mann -Whitney U. Non-equivalent groups Eg Sick vs Healthy

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Single Factor Research

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  1. Single Factor Research

  2. If I want to test the efficacy of a new drug on blood pressure then I have some choices of design….

  3. Two independent samples • Control vs drug groups (random assignment) • Comparison is independent t- test • Or Mann -Whitney U

  4. Non-equivalent groups • Eg Sick vs Healthy • Male vs female…. • Comparison is independent t- test • Or Mann -Whitney U

  5. Matched design. • Pairs of twins sign up for study • One twin is in control group the other in drug group • Comparison is paired t-test • Or Wilcoxon

  6. Repeated design • Take a baseline measure of BP for each subject • Then give drug • Repeated (paired) t-test • Wilcoxon

  7. CONTROL GROUPS – provide baseline for comparison

  8. No treatment • Compare treatment vs no treatment • (no treatment only difference is variable of interest) Standard control for : • Situational • Task or • Instructional difference

  9. Placebo • Standard for drug trials • Or obvious clinical treatments • Inert substance given for comparison • Tests the protocol • Tests the beliefs of treatment

  10. Waiting List • If no treatment or placebo are unethical or not possible then assign subjects to waiting list. • Must be done randomly (not first come first serve)

  11. Yoked • Executive Monkey Experiment • Two monkeys ‘yoked’ together • Executive controls off switch the other is helpless • Both get shocked equally

  12. Only two levels Advantage • Simple • Direction of difference obvious Disadvantage • Deceptive appearance of linearity • Single hypothesis test

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