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