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Scientific Method and Experimental Design
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Scientific Method and Experimental Design


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  • 1. Scientific Method and Experimental Design
  • 2. Goal of Science Steps of Scientific Method Hypothesis Independent and Dependent Variable Experimental Design Sample Size and Validity Data Collection and Organization Conclusions The Characteristics of Science
  • 3. Science A process, based on observations and experimentation, that provides explanations of natural events or problems Uses the scientific method Conclusions rely on data and facts, inferences and observations
  • 4. Steps of the Scientific Method
    • Make observation
    • Question/problem
    • Background research
    • Hypothesis
    • Experiment/observe
    • Collect and analyze data
    • Conclusion
    • Retest
    • Publish
  • 5. An possible explanation of a natural event or observation that can be tested by additional observations or experimentation Must be testable! Written as “If……., then……” statement Hypothesis
  • 6.
    • Identify 2 crucial variables to write hypothesis
    • Independent variable : The factor that is deliberately manipulated in an experiment (also called experimental variable)
      • “ Presumed cause”
    • Dependent variable : The variable that changes in response to changes in the independent variable. It is what is measured in the experiment
      • “ Presumed effect or result”
  • 7. Hypothesis
    • Hypothesis is written as follows:
      • If independent variable , then dependent variable
      • Ex. If 100 grams of fertilizer is applied to a lawn, then the lawn will grow at a faster rate.
      • IV amount of fertilizer
      • DV rate of growth
  • 8. Controlled Experiments Tests one variable at a time (experimental variable) Controlled experiments include 2 groups: Experimental Group Exposed to experimental variable Control Group Not exposed to experimental variable, all variables held constant All extraneous variables must be held constant in both groups!
  • 9.
    • Sample Size (N)
    • The number of subjects involved in experimentation
    • Increasing N
      • Decreases impact of chance events and error
      • Increase reliability of results (validity)
    Sample Size
  • 10. The extent to which experimental results can be generalized to other settings or situations To increase validity, increase N Ex. 7 tanks, 6 experimental and 1 control Each tank has 100 single celled green organisms All variables held constant except the light Validity
  • 11. Quantitative Data: numerical data Ex. Measurement of depth in inches Qualitative Data: descriptive data collect with your senses Ex. Color Use data tables and charts to more effectively display data for analysis Record and Analyze Data
  • 12. Conclusion Refers back to the hypothesis “ Supported” or “rejected” Use data to support If the same conclusions are supported over a long enough period of time they become theories
  • 13. Scientific Theories Explanation for a natural event Based on observation, experimentation, inference, and evidence Explains current observations and predicts future events
  • 14. The Characteristics of Science
    • Based on the assumption that the natural world can be investigated and explained in terms we can understand.
    • Based on the results of controlled experimentation and observations.
    • The results must be repeatable and verifiable.
    • Must be refutable. If a hypothesis is not supported by evidence it must be rejected or re-worded
  • 15.