Designing A Controlled Experiment

 Some discoveries happen by chance but the standard is for a scientist to begin with forming a question.  The more limited the question, the easier it is to set up an experiment to answer it.

 Take an educated guess, hypothesis, about the answer to the problem or question.  A hypothesis uses your prior knowledge and observations to predict what will happen and why.

 Identify variables and constants.  Variables and constants are factors you think could affect the outcome of your experiment.

 In a controlled experiment there are two types of variables:  Independent Variable (Manipulated Variable): The factor you want to test. It is changed by the investigator to observe how it affects a dependent variable.  Dependent Variable (Responding Variable): The factor you measure or observe during an experiment. A. Variables

 To test how the independent variable affects the dependent variable, you need to keep all other factors the same for each test.  Constants: The factors that remain the same.  Without constants two independent variables could change at the same time and you won’t know which variable affected the dependent variable. B. Constant (Controls)

 Reporting of the data should state specifics of how the measurements were calculated.  A graduated cylinder needs to be read with proper procedures.  Proper technique gives validity to the data.  Graphing Data: Graphing takes numbers and shows patterns that you might not notice.

 Describe trends you see in the data.  Compare the results to your hypothesis.  Use evidence in your results to support your conclusion.

 Error is part of any scientific research.  Document anything that you changed in your procedure.  Be sure to include unanticipated factors or accidents that may have influenced your results.  Offer alternative explanations for your results if necessary.  The End