Scientific Experiments Follow Rules An experimenter changes one factor and observes or measures what happens.
The ControlVariable/GroupThe experimenter makes a special effort to keep other factors constant so that they will not effect the outcome. Those factors are called control/constant variables.
What is the Purpose of a Control? Controls are NOT being tested Controls are used for COMPARISON
Other Variables The factor that is changed is known as the independent variable. The factor that is measured or observed is called the dependent variable.
Example of Controls & Variables For example, suppose you want to figure out the fastest route to walk home from school. You will try several different routes and time how long it takes you to get home by each one. Since you are only interested in finding a route that is fastest for you, you will do the walking yourself.
What are the Variables in Your Experiment? Varying the route is the independent variable The time it takes is the dependent variable Keeping the same walker throughout makes the walker a control variable.
One more thing… it is bestto make several trials witheach independent variable.
Remember: To be a Valid Experiment: Two groups are required --- the control & experimental groups There should be only one variable
Data Results of the experiment May be quantitative (numbers) or qualitative
Data Must be organized Can be organized into charts, tables, or graphs
Conclusion The answer to the hypothesis based on the data obtained from the experiment Formulating a generalization about the results, which may accept, reject or modify a hypothesis
RetestIn order to verify the results,experiments must be retested.
Sample ProblemsLets say I have a problem: My car wont start. How would I use the scientific method to solve this problem? Problem: My car won’t start. I want it to start. Hypothesis: If I put gas in my car, it will start. Materials: 5 gallon gas can, 5 gallons gasoline, money to buy gasoline, a ride to the gas station Experiment: First, I will call my friend Bill and ask for a ride to the gas station. I will take the five gallon gas can and fill it with five gallons of gasoline at the pump. After paying the gas station owner for the gasoline, I will get a ride back to my car and put the gasoline in the tank. Once the gasoline is in the tank, I will attempt to restart the car. Results: The car started on the first try. Conclusion: When I put gas in my car, it started.
Mr. Smithers believes that a special juice will increase the productivity of workers. He creates two groups of 50 workers each and assigns each group the same task (in this case, theyre supposed to staple a set of papers.) Group A is given the special juice to drink while they work. Group B is not given the special juice. After an hour, Mr. Smithers counts how many stacks of papers each group has made. Group A made 1,587 stacks, Group B made 2,113 stacks. The control group of this example is Group B, because they are not given the special juice. They are just there for explaining the results. The experimental group of this example is Group A, because they are given the special juice. This is the factor that you are experimenting on.
Question Independent Dependent Controlled Variable Variables Variables (What I (What I (What I keep Change) Observe) the same)Who listens to The groups The amount of Ask themusic the receiving the time that each question inmost: survey: person listens exactly theteenagers or teenagers or same way to to music pertheir parents? parents each individual day measuredHow fast does a Time measured in hours Height of candle • Use samecandle burn? in minutes measured in type of centimeters at candle for regular intervals every test of time (for • Wind--make example, every sure there is five minutes) none
Solving a Problem1) Identify a Problem2) State Observations about the problem3) Form a Hypothesis about the problem (if…then…)4) Design an Experiment to test the hypothesis5) Collect Data6) Form a Conclusion7) Retest