The Scientific Process

Step 1 – Define the Problem (or State the Question) This is based on an observation (any information gathered with your senses) Example: Gas is expensive. What type of gas goes farthest?

Step 2: Hypothesis - an educated guess A hypothesis is a tentative explanation that accounts for a set of facts and can be tested by further investigation. Ask your neighbor what kind of gas they think goes the farthest. Example: Premium gas will go the farthest.

Step 3: Test the hypothesis This can be done by observation or by an experiment A good experiment only tests 1 variable (something that changes)

Step 3: Test the hypothesis A good experiment must have: A) A Control - the basis of comparison - Almost always comes first in the experiment. - It’s what you compare the results to. Example: record how far you go with regular gasoline.

Step 3: Test the hypothesis  A good experiment must have: B) An Independent Variable -the thing that is manipulated (changed) by the scientist - This is the thing that is being tested. - This is what I change. - Everything but the I.V. must remain constant. Example of I.V.: the other types of gasoline. Examples of constants:

Step 3: Test the hypothesis  A good experiment must have: C) A Dependent Variable -something that may change because the I.V. was changed -This is the result of the experiment (the outcome). Example: what changed as a result of the gas being changed? the distance traveled D) Multiple Trials: Repeat the experiment.

Step 4: Analyze the Data Usually done with charts, tables, and graphs Example: record and compare the distances traveled.

Step 5: Draw Conclusions -Always based on analysis of data. -Often leads to new questions and hypothesis Example: premium gasoline goes the farthest.

Bobby notices that his tomatoes are not growing very fast so he decides to test the effect of earth worms on plant growth. He thinks that adding earth worms to his garden soil will make them grow taller so he conducts an experiment. He plants tomatoes in 2 pots. He does not put worms in the first pot and put 5 worms in the second pot. He puts the plants in the same window and waters them the same amount every day. Each day he measures how high the plants have grown. What observation led to the experiment? What is the hypothesis? What is the control? What is the independent variable? What is the dependent variable? The pot with the worms grew 10 inches taller. What else must be done to validate the experiment?

Concluding Remarks… A basic assumption of science is that the world is understandable. Science is based on evidence – both observational and experimental. Only hypotheses that are testable are valid. A hypothesis can be supported, modified, or rejected based on collected data Experiments are designed to test hypotheses.