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Now featuring the PREP Handbook with activities using Arabidopsis thaliana.
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Nadja Anderson, Ph.D
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The Scientific Method used in an everyday situation
You arrive home late at night, walk up to your house door, unlock the door, reach in to the light switch just inside the front door.
The light does not come on! Now what?
As a normal human being, you will go through a mental and physical process of hypothesis testing. The steps happen very rapidly in your mind and, prior to this, you may not have had names for the various steps, which are very much the scientific method.
Observation: Darkness, Switch On, No Light
....still dark
Question: Is the Power Out?
Hypothesis/Prediction: If power is out, then lights will be out at all the neighbors when I look .
Experiment: Observation of neighborhood lights (indirect evidence)
Analysis: If ANY house has lights, prediction fails, conclusion = reject hypothesis?
Possible error: Coleman Lantern, Generator
If all houses dark, prediction holds, conclusion = do not reject hypothesis?
Possible error: All out to dinner?
Conclusion: no lights in neighborhood, note chance error = no definitive answer!
Revised experiment: Try another lamp in the house, with a revised hypothesis/prediction: If the power is out then none of the lamps in the house will turn on.
Analysis: If lamp works, prediction fails,
conclusion = reject hypothesis.
If lamp does not light, prediction is supported,
conclusion = does not reject hypothesisQuestion: Is light bulb burned out?
Hypothesis/Prediction: If bulb is burned out, then the old bulb will not light another lamp
Experiment: Install old bulb into another lamp.
Control Experiment: Determine that a new bulb lights the other lamp.
Analysis(1): Original bulb does not light both lamps
Conclusion: Evidence supports hypothesis, does not reject hypothesis
Or
Analysis(2): Old Bulb does light other lamp
Conclusion: Hypothesis is rejected, old bulb is not burned out. Start with new question#
New Hypothesis for Analysis(1): If old bulb is burned out, then lamp will turn on when a new bulb is installed in the lamp.
Analysis: Light comes on, supports hypothesis,light does not
#New Question: Is lamp plugged in?
Hypothesis: Lamp should turn on if plugged in properly.
Experiment: Check if light is plugged in, turn on lamp…
Control Experiment: Plug in another lamp that is known to function
Analysis: If lamp turns on, hypothesis is supported.
If both lamps do not turn on,
Revised Hypothesis: Lamps will not function if the outlet is not functional. (If only the other lampworked in the original outlet, then it is time to ask a new question*)
Prediction: Lamp will function in another outlet
Experiment: Plug lamp into another outlet.
Control Experiment: Use outlet that functions with another lamp.
Analysis: If lamp turns on,
*New Question: Is the lamp functional?….and so on.
Now let's look at the use of the Scientific Method in a research experiment.....
