Hypothesis Controlled Experiment and Variable Independent and Dependent Variable Sample Size and Validity Scientific Method and Experimental Design
Steps of the Scientific Method <ul><li>Make observations. </li></ul><ul><li>Ask a question. </li></ul><ul><li>Form a hypothesis. </li></ul><ul><li>Test the hypothesis. </li></ul><ul><li>Analyze the results. </li></ul><ul><li>Draw conclusions. </li></ul><ul><li>Communicate the results. </li></ul>
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
<ul><li>Sample Size </li></ul><ul><li>Sample Size (N) </li></ul><ul><li>The number of subjects involved in experimentation </li></ul><ul><li>Increasing N </li></ul><ul><ul><li>Decreases impact of chance events and error </li></ul></ul><ul><ul><li>Increase reliability of results </li></ul></ul>
Why does a good experiment need to have two parts, including a control? <ul><li>It isolates and tests the effects of one variable at a time </li></ul><ul><li>Provides certainty that the change is due to the effect of the variable being tested </li></ul>
Validity The extent to which experimental results can be generalized to other settings or situations To increase validity, increase N
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