Experimental Design. Purpose/Objective Statement of the problem or question to be answered Usually...
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Transcript of Experimental Design. Purpose/Objective Statement of the problem or question to be answered Usually...
Experimental Design
Purpose/Objective
• Statement of the problem or question to be answered
• Usually this involves an observation of some type of phenomenon
• What is the difference between an observation and an inference?
Observation vs. Inference?
When Ms. Moracco comes home from school, her dog Chesney’s tail is moving back & forth. He jumps up & down, barking rapidly. He is happy to see her.
Background/Research
Information already known or researched
Should come from RELIABLE sources (e.g. wikipedia is not an example - ever in this classroom!!!)
Hypothesis
• Testable statement which may be falsified• Written as if…then statement where the
independent variable follows the if and the dependent variable follows the then.
• Independent variable- The factor/condition being tested or changed purposely by the experimenter
• Dependent Variable- the factor/condition being measured or that changes as a result of the independent variable
Misconception Alert!!!
Hypothesis Educated
Guess
Experiment
• Materials- list of all equipment necessary • Procedure - step-by-step description of
how to the experiment…should be reproducible by anyone wishing to replicate your results.
Experiment Con’t.
• Constants- factors/conditions that are kept the same in both the experimental and control groups
• Control Group- “normal”/non tested group; standard for comparison; Nothing is done to this group
Example
• How bright is right?• An automobile manufacturer wants to know how bright
brake lights should be in order to minimize the time required for the driver of a following car to realize that the car in front is stopping and to hit the brakes.
• What is the independent variable? • (brightness of brake light) • What is the dependent variable? • (time to hit brake)
Data
• Qualitative - categorical; warm & fuzzy; not reproducible (e.g. blue, hot, cold)• Quantitative - direct measurements with
correct units (e.g. temperature, time, distance)
Analysis
• A detailed record of all observations (data tables, graphs, etc.) & a summary or explanation of those observations
Conclusion
• A final statement of whether or not the original hypothesis was supported or not
• Evaluation of human error…In other words what did you do wrong?
• Then what?
Facts, Proof, Theories & Laws
• Fact: Observation confirmed over & over (change more often than theories!!!)
• Proof: NOTHING in science is proven. This word does not belong in science. Send this word to your math teacher!
• Theories are an explanation of a natural phenomenon that is supported by a large body of scientific evidence obtained from many observations, experiments and laws.
• A law is a generalized description of a fact of nature about what has happened from which we can generalize what we think will happen or how something behaves under certain circumstances. E.g. An apple falls to the Earth because of the Law of Gravity.
Misconception Alert!!!!
Theory Law
Revisiting Theories
Theories are explanations - look at the diagram……
Facts
Laws
Inferences
Tested hypotheses
Explanation
Theories vs. Laws - quick review
Theories are Laws are
Based on evidence Based on evidence
Tested Tested
Effective in Problem SolvingExplanation of how Explanation of what
will happen
Words of Experimental Design
Observation/Inference Hypothesis Procedure Constant Control Variables (two kinds) Data (two kinds) Fact Hypothesis Law Theory