Scientific Method and Experimental Design
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Scientific Method and Experimental Design

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    Scientific Method and Experimental Design Scientific Method and Experimental Design Presentation Transcript

    • Scientific Method and Experimental Design
    • 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
    • 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
    • Steps of the Scientific Method
      • Make observation
      • Question/problem
      • Background research
      • Hypothesis
      • Experiment/observe
      • Collect and analyze data
      • Conclusion
      • Retest
      • Publish
    • 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
      • 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”
      Hypothesis
    • 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
    • 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!
      • 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
    • 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
    • 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
    • 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
    • Scientific Theories Explanation for a natural event Based on observation, experimentation, inference, and evidence Explains current observations and predicts future events
    • 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
    •