Scientific Methods

Science questions Testable Specific

Hypothesis

Hypothesis—which is better, best? “Water levels affect the amount of lice suffered by rainbow trout.” “Rainbow trout suffer more lice when water levels are low.” “Rainbow trout suffer more lice in low water conditions because there is less oxygen in the water.”

Prediction Restate your hypothesis in terms of what you expect to happen. Educated guess

Experimental Design elements Precise Step by step Detailed enough for another scientist to duplicate your experiment Can another scientist reproduce your results?

Variables Manipulated variable—the one you change Responding variable—should give you data to answer your original question Controlled variables—held constant/not changed

Analyze and interpret data Table Graph Write about the averages, highs and lows

Conclusion Summarize your results in a few sentences. Include key facts from your background research to help explain your results as needed. State whether your results support or contradict your hypothesis Errors in experiment Ways to improve the experiment

Tricky Terms

Qualitative vs. Quantitative Qualitative (quality) uses descriptive words Quantitative (quantity) uses numbers and measurements

Hypothesis vs. Inference vs. Theory Hypothesis—testable statement/expectation about the experiment Inference—a conclusion based on past experience/knowledge Theory—LOTS of experiments that agree in their results, the hypothesis becomes a theory

Controlled experiment Only one variable is manipulated Results can be related back to the single variable, so the results are valid

Controlled variables Things that are held constant or kept the same in the experiment Like the swabbing methods you developed as a class for the bacteria lab There are many controlled variables in an experiment

Control The part of the experiment that is not experimented on I put one clean petri dish in the incubator to make sure nothing grew on it This made sure the agar was clean/sterile