Scientific Method and Experimental Design
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Transcript of Scientific Method and Experimental Design
Scientific Method
Hypothesis
Controlled Experiment and Variable
Independent and Dependent Variable
Sample Size and Validity
Scientific Method and Experimental Design
Steps of the Scientific Method
1. Make observations.
2. Ask a question.
3. Form a hypothesis.
4. Test the hypothesis.
5. Analyze the results.
6. Draw conclusions.
7. Communicate the results.
Hypothesis
An explanation of a natural event or observation that can be tested by additional observations or experimentation
Example of Hypothesis
Observation: The population of tiger salamanders declined 65% between 1984 and 1988
Hypothesis: Acids that were formed in the upper atmosphere by pollutants were falling onto mountains in the winter snows
Controlled Experiment and Variable
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
Independent and Dependent Variables
Independent variable: The factor that is deliberately manipulated in an experiment (also called experimental variable)
Dependent variable: The variable that is changed or determined by manipulation of the independent variable. It is what is measure in the experiment
Sample Size
Sample Size (N)
•The number of subjects involved in experimentation
•Increasing N
• Decreases impact of chance events and error
• Increase reliability of results
Validity
The extent to which experimental results can be generalized to other settings or situations
To increase validity, increase N