Experimental Design Notes

Testable Questions A question that can be answered through experimentation. Testable: we have the tools to answer the question, and it is possible to answer the question Non-testable: a question that is not answerable through experimentation: HOW or WHY questions.

Easy Testable Questions Broad Questions (lead to science reports NOT experiments) Testable Questions (lead to experiments) How do plants grow? What amount of water is best to grow tomatoes? or What type of soil is best to grow petunias? or What amount of sunlight is best to grow daffodils? What makes something sink or float? How well do different materials sink or float in water? How do rockets work? How does changing the shape of a rocket’s fins change its flight? How does the sun heat up water? Does the sun heat salt water and fresh water at the same rate? What happens when something freezes? Do different liquids freeze at the same rate? What makes cars move? How does the surface on which a car moves affect how fast it goes? How do batteries work? Which type of battery lasts the longest? What makes a magnet attract things? Does temperature have an effect on a magnet’s strength? Why does ice melt? What is the best insulator to keep ice from melting?

Experimental Hypothesis a testable explanation for a question or theory.

Experimental Hypothesis Format: Always write your hypothesis in the format: If we do this, then this will happen, because . . . we do this: – how you will change the independent variable for both groups this will happen: - tell what will happen to the dependent variable in both groups Then – next Than – comparison because – explain why that should occur

Write your own hypothesis for the following question: What is the effect of applying MiracleGro to plants?

Variable: anything that can change Control group – a group with no variables changed; used for comparison Experimental group – the group in which you change a tested variable Constants/controlled variables – factors that stay the same throughout all experiments EVERYTHING must stay the same except the independent variable.

What is the control group in our Miracle Gro experiment? What is the experimental group? What do we need to keep constant?

Independent variable- tested variable that can affect the outcome of the experiment (what you change) Dependent variable – variable that changes as a result of the independent variable (depends on independent variable); the variable that you measure; (the result)

What is the independent variable in the Miracle Gro experiment? What is the dependent variable?

Results Quantitative: data that can be measured and written as numbers Qualitative: results that can’t be written as numbers; descriptive results

Reliability – The experiment is repeatable and will produce the same results. If another person performs the experiment in the same conditions, they will receive the same results. Validity – how well your experiment is performed – - does it test what you intend to test? - did you collect enough data? - did you use the correct equipment and use it correctly?

Conclusion 3 parts: Claim Evidence Explanation/Reasoning

Claim – A statement that answers the question   Evidence – Quantitative data or Qualitative observations that support the claim Explanation/Reasoning – Show how evidence supports the claim - Use scientific principles you have been learning to explain the relevance and importance of the data - Why? (or because)