chapter 1: the scientific method

The Driving Question

• Provide the reason for experimenting.
• What can be learned or reinforced by the experiment?
• Example = Does light affect the growth of sunflowers?

Research

• Before you begin your experiment, you will need to do research.
• Research gives you vital information on what is:
  • Already known on the subject you are researching.
  • What is not known about the subject you are researching.
  • Whether your experiment has been done.
  • How your experiment may expand on previous research.
• Research shapes your experimental design.
• Research is essential if you want to do good scientific experimentation.

Observation

Hypothesis

• Predicts what you think the outcome of the experiment will be.
• A hypothesis only predicts what may happen; it does not explain why it may happen.
  • A hypothesis is NOT simply a guess; it is a testable explanation of your observations and inferences.
• Example = If the six sunflower seeds receive 10 hours of sunlight, then they will grow faster than the six seeds that receive 5 hours of sunlight and no sunlight.

Variables

• Independent variable (IV)
  • The ONE variable you change and test.
  • There can only be one IV in an experiment
  • Sometimes placed on the x-axis of a graph.
    • Example = When testing the effects of light on plant growth, the IV is the amount of light
• Dependent variable (DV)
  • Results or the variable that changes in response to the independent variable.
  • The observation you are waiting to record during an experiment
  • Placed on the y-axis of a graph
    • Example = When testing the effects on the amount of light on sunflower growth, the DV is the amount of growth
• Control Variable
  • A variable that does not change during an experiment. 
  • You must keep all factors the same every trial.
    • Examples = Type of plant, temperature, the moisture of the soil.

Experiment

• A good experiment has two groups: a control group where the independent variable is left alone, and an experimental group where the scientist manipulates the independent variable (there may be more than one experimental group).
  • Control Group
    • The group that does not receive the IV.
    • The group that has nothing done to it. It is used as a baseline to compare test vs. normal conditions.
    • If we were testing the effects of fertilizer, it would be the group that does not receive fertilizer.
    • In the sunflower lab, there is no control group but there is a comparison between the three light conditions.
  • Experimental Group
    • The group that receives the independent variable.
    • If we were testing the effects of fertilizer, it would be the group that does receive fertilizer.
    • In the sunflower example, all three plants are in the experimental group.

Data and Data Analysis

Conclusion

• Written in paragraph format
• Comprises three parts:
  • Claim
    • Summarizes the results of the experiment.
    • Example = The plant grew the most when it received 10 hours of light daily.
  • Evidence
    • Summary of the key quantitative points in the experimental data.
    • NEVER, EVER write, “Look at the data/graph/table” or any version of this.
    • Example = The plant that received 10 hours of light daily grew 6 cm over a five day period, while the plant that received 5 hours of light grew 2 cm and the plant that received no light did not grow. 
  • Reasoning
    • Why you think you got the results.
    • Inference based on your prior knowledge/research/information you have learned in class.
    • Okay example = Plants that received more light are able to make more food that is used for growth.
    • Good example = Plants need light in order to convert light energy into sugars.  The more sugar the plant makes, the more usable energy it has to grow.