The Scientific Method

The Process of Science 1. Careful Observation 2. Question 3. Formulate a Hypothesis 4. Make a Prediction (“if-then” statement; assume the hypothesis is correct and predict the result of a test) 5. Test (collect data) Experimental group -receives the treatment/condition Control group -business as usual; does not receive treatment Independent, dependent and controlled variables 6. Conclusion (if prediction does not occur, then hypothesis is falsified; if prediction occurs, hypothesis is supported)

Question Well defined Testable Measurable Controllable Reasonable and consistent with existing bodies of knowledge

Consider These Questions Are serial killers evil by nature? What is the cause of AIDS? Why is grass green? What is the best recipe for chocolate chip cookies? When will the big earth quake hit San Francisco?

Hypothesis Testable Falsifiable Written as a statement

Which of the following is a useful scientific hypothesis? Plants absorb water through their leaves as well as their roots. Mice require calcium for developing strong bones. Dogs are happy when you feed them steak. HIV can be transmitted by cat fleas.

Tests Have Variables Dependent Independent Controlled The variable measured, counted, or recorded. Placed on y-axis of a graph Independent What the investigator deliberately varies or manipulates during an experiment. Chosen because it is thought to affect the dependent variable Placed on x-axis of graph Controlled Variables or factors that are kept equal in all treatments.

Identify the D and I variables Mice are kept at different temperatures for 6 weeks. Percent weight gain is recorded. A hypothesis proposes that dog weight increases with fewer litter mates. Seeds are soaked in salt solutions of different concentrations and germination is counted each day. The diversity of coastal algal species is calculated before and after an oil spill.