Steps of the Scientific Method

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Steps of the Scientific Method
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1. State the Problem

• What problem are you trying to solve?
• Normally stated as a question.
• EXAMPLE Will giving plants Brand X fertilizer
  every day for thirty days increase their growth?

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2. Research the Problem

• The researcher should gather as much information
  about the problem as possible.
• The researcher should consult scientific journals
  (magazines) or experts in the field. (must be
  reliable sources)
• EXAMPLE Brand Z fertilizer is similar in
  composition to Brand X but does not contain
  phosphorous, and studies have demonstrated the
  effectiveness of Brand Z. Studies have also
  shown that phosphorous may increase plant growth.

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3. Form a Solution, or Hypothesis

• Make an educated guess as to what will solve the
  problem.
• Write the hypothesis as an if-then statement if
  possible.
• The hypothesis must be TESTABLE!
• EXAMPLE If Brand X fertilizer is added to plants
  every day for 30 days, then they will grow taller
  than plants grown without it.

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4. Conduct an Experiment

• EXAMPLE Add Brand X fertilizer to 100 plants
  every day for 30 days to determine if they grow
  taller than plants grown without it.
• Variables are conditions that change, or vary,
  throughout an experiment.

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Independent Variable (I.V.)

• I change the Independent variable.
• This is the one and only variable that the
  experimenter changes from one group to another.
• EXAMPLE Whether or not the plants receive Brand
  X fertilizer is the Independent variable because
  I, the experimenter, control which plants receive
  the fertilizer. I do not control how tall the
  plants grow.

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Dependent Variable (D.V.)

• The response to the independent variable.
• It is not under the experimenters control.
• EXAMPLE The dependent variable is the height of
  the plants because it changes based upon whether
  or not the plants received Brand X fertilizer
  (I.V.) and is not under the control of the
  experimenter.

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Experimental Group

• The group or subject that receives the
  independent variable.
• EXAMPLE The plants that receive Brand X
  fertilizer are in the experimental group.

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Control Group

• The group or subject that does not receive the
  independent variable.
• The control is used to compare data with the
  experimental group.
• EXAMPLE The group that does not receive Brand X
  fertilizer is the control group. The height of
  the plants grown with Brand X fertilizer
  (experimental group) will be compared to the
  height of the plants grown without Brand X
  fertilizer (control group) to determine if Brand
  X fertilizer has an effect on plant height.

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Constants

• Constants are conditions that remain the same
  between the experimental and control groups in an
  experiment.
• To determine whether the independent variable is
  causing the result, all other variables must
  remain constant.
• EXAMPLE To determine whether adding Brand X
  fertilizer is causing a difference in plant
  height, all plants must receive the same amount
  of sunlight, amount of water, type of soil,
  temperature, pot size, humidity, CO2, etc.

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Sample Size

• Sample size refers to the number of subjects
  exposed to the independent variable.
• The larger the sample size, the more valid the
  results.

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5. Record and Analyze the Data

• Data is typically recorded into data tables.
• Then, the data is graphed to increase
  understanding and visual appeal.
• EXAMPLE

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6. State a Conclusion

• Look at your results to determine what they mean.
• Determine whether your hypothesis is correct.
• It is acceptable for your hypothesis to be wrong.
  An incorrect hypothesis can give you as much
  information as a correct one.
• EXAMPLE The data suggests that adding Brand X
  fertilizer to plants every day for thirty days
  increases plant height.

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7. Repeat the work

• This is the most important step in scientific
  inquiry.
• If you only conduct the experiment once, your
  results may be written off as a fluke.
• Repeating the same results from different
  experiments lends them validity.
• Different results suggests that you should go
  back to the drawing board.