1. Hypothesis Controlled Experiment and Variable Independent and Dependent Variable Sample Size and Validity Scientific Method and Experimental Design
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3. Hypothesis An explanation of a natural event or observation that can be tested by additional observations or experimentation
4. 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
5. 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
6. 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
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9. Validity The extent to which experimental results can be generalized to other settings or situations To increase validity, increase N