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The Basics of Experimental Design

The Basics of Experimental Design. Gregory M. Williams, Ph.D. Hudson Regional Health Commission. Overview. Why? Scientific Method Analysis Example Questions. Why do Research?. To answer questions To publish For money Personal satisfaction. The Scientific Method.

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The Basics of Experimental Design

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  1. The Basics of Experimental Design Gregory M. Williams, Ph.D. Hudson Regional Health Commission

  2. Overview • Why? • Scientific Method • Analysis • Example • Questions

  3. Why do Research? • To answer questions • To publish • For money • Personal satisfaction

  4. The Scientific Method A series of steps for conducting scientific research

  5. The Scientific Method • Observe • Question • Guess • Test • Conclusions • Retest

  6. Example • Discovery and testing of a new mosquito larvicide.

  7. Observations • You are always observing • Look at the data • Traps • Larval surveillance • Infection rates • Weather You notice that there are never any mosquito larvae in outdoor ashtray.

  8. Question • As you Observe you are faced with questions • Why is my data the way it is? • Pick a question to test • Question should be yes/no Does water in ashtray act as a larvicide?

  9. Literature Review • What have others done? • Check relevant journals • JAMCA, JME, VBZD, JVE • Learn • larvicidal bioassay • Don’t want to repeat Search for keywords-ashtray, tobacco, nicotine, mosquito…

  10. Form a Hypothesis • What is answer? • Prediction • “If…then” logic If ashtray water contains a larvicidal compound…then it should kill larvae placed in it.

  11. Hypothesis • Explanation • Reflect experience • Multiple hypotheses • Environmental conditions • Oviposition deterent • Must be testable

  12. Design the Experiment • Identify the variables • Independent • What you are testing • Ashtray water • Dependent • What you measure • Larval mortality

  13. Design the Experiment • Experimental groups • Treatment group • Receives the treatment • Larvae in ashtray water • Control group • No treatment • Otherwise identical • Larvae in plain water • Normalize conditions • Temp, light, containers, etc.

  14. Experiment • Test your hypothesis • Replication • More is better!

  15. Analyze the Results • Statistics • Calculations to determine how good data are • Are results real or chance? • Compare deviations to results • Treatment vs. control

  16. Draw Conclusions • No difference between trt. & con. or con. > trt. • Ashtray water is not larvicidal • Mortality of trt. > con. • Ashtray water is larvicidal

  17. Follow-up • What compound in the ashtray water is acting as larvicide? • Nicotine, sand, other… • Is the effect dose dependent? • Does this hold true for other ashtrays?

  18. Closing Thoughts Each answer leads to more questions!

  19. Questions?

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