Stages of Experimental Inquiry

Carl J. Wenning, Coordinator

Physics Teacher Education

Illinois State University

Five Stages of Experimental Inquiry

1. Observation & Identification

2. Experimentation:a) Observational

b) Testing

c) Application

3. Generalization

4. Verification

5. Communication

1. Observation & Identification

Systematic observations lead to different types of questions to be resolved: Why? How? What if?

A well-formulated research question is derived from current knowledge

2a. Experimentation

Plan the experiment Gather evidence from observations Create an evidence-based relationship, test

and explanation, or find an application

2b. Experiment Types

Observational (experiment to investigate a new phenomenon.)

Testing (experiment to test a hypothesis or model.)

Application (experiment to solve a practical problem or determine a physical quantity in two independent ways.)

2b1. Observational Experiment

“You have a sealed hollow metal sphere with an unknown gas inside. You also have a thermometer, a pressure gauge, a hot plate, some ice and a container holding water. Design and conduct an experiment to determine if there is a relationship between pressure and temperature of the unknown gas when its volume is kept constant.” (PAER Group, Rutgers U.)

2b2. Testing Experiment “Design and conduct an experiment to test

the following rule: an object always moves in the direction of the net force exerted on it. You have a dynamics cart, dynamics track, a spring scale, masking tape, a bowling ball, a mallet, a small ball and cushion to use. You may also use any other common equipment available in the lab. Feel free to use your lab partner as an object!” (PAER Group, Rutgers University)

2b3. Application Experiment

“Design and conduct at least two independent experiments to determine the coefficient of static friction between your shoe and the sample of carpet/linoleum provided. Equipment: spring scale, ruler, protractor, carpet or wood surface, tape.” (PAER Group, Rutgers University)

3. Generalization

Depends upon type of experiment Observational - typically a relationship is

derived from a graph; a hypothesis or model might be generated for further experimentation

Testing - typically evidence is determined to support or disconfirm a model or hypothesis; data never “proves” a model or hypothesis

Application - either it works or it doesn’t Be careful not to overextend generalization

4. Verification Depends on type of experiment

Observational - Use new formulation to make predictions for verification

Testing - Use hypothesis or model to deduce predictions for verification

Application - Either it works or it doesn’t Consider statistical probability Consider other explanations if hypothesis

or model is basis of prediction

5. Communication Recall that science is a social compact, and that

there are accepted avenues and processes for communicating results

Recall that evidence only supports of disconfirms, never “proves”

Your credibility is on line Remember to limit your generalizations Communication provides evidence as well as

procedures so that others can replicate your findings

Generic Experimental Design

Identify the system to be studied Identify and distinguish system variables Identify general procedures to follow Identify the model if possible Choose range of the independent variable Collect and interpret data Consider overall precision of experiment

References

For types of experiments including additional procedures, visit PAER Group at Rutgers University:

http://paer.rutgers.edu/ScientificAbilities/Formative+Assessment+Tasks/default.aspx

ISU Student Lab Handbook: http://www.phy.ilstu.edu/slh/