Scientific Method

Steps in the Scientific Method Observation Hypothesis Experiment Data Collection Conclusion Retest

Observations Gathered through your senses A scientist notices something in their natural world

Observations An example of an observation might be noticing that many salamanders near a pond have curved, not straight, tails

Hypothesis A suggested solution to the problem. Must be testable Written as If…Then… statements Predicts an outcome

Hypothesis An example of a hypothesis might be that if there is pollution in the soil, then a salamander will have a curved tail.

A procedure to test the hypothesis. Experiment A procedure to test the hypothesis. Can be an experiment, model, or observation

Variable – factor in the experiment that is being tested Parts of an Experiment Variable – factor in the experiment that is being tested

Experiment A good or “valid” experiment will be repeatable and change only one variable at a time

Experiment A good experiment will also have many replicates (individuals) n=sample size

Experiment

Controls,Variables, and Constants

Scientific Experiments Follow Rules An experimenter changes one factor and observes or measures what happens.

Constants The experimenter makes a special effort to keep other factors constant so that they will not effect the outcome.

Controls Controls establish a “status quo” That’s how conditions are under normal circumstances.

What is the Purpose of a Control? Controls are NOT being tested Controls are used for COMPARISON

Independent Variable The factor that is changed by the experimenter is known as the independent variable. Its effects are measured by changes in the dependent variable It will be graphed on the X- AXIS

Dependent Variable The factor that is measured or observed is called the dependent variable. Observed and measured during the experiment Graphed on the Y-AXIS

Graphing Variables

Example of Controls,Variables, and Constants 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 constant. There is NO CONTROL.

One more thing… it is best to make several trials with each independent variable.

Valid Experiments

Remember: To be a Valid Experiment: Two groups are required --- the control & experimental groups There should be only one variable each experiment

Data Results of the experiment May be quantitative (numbers) or qualitative (descriptive)

Data Must be organized Can be organized into charts, tables, or graphs

What are trends in graphs? Negative (inverse) When one increases, the other decreases Positive (direct) When one increases, the other increases OR when one decreases, the other decreases No relationship One has NO EFFECT on the other.

Conclusion The answer to the hypothesis based on the data obtained from the experiment

Why do scientists repeat experiments? In order to verify results, experiments must be RETESTED! It adds validity to the findings.

How do scientists communicate findings? When scientists want to communicate the results of their experiment, they use SCIENTIFIC JOURNALS or other publications!

What is pure and applied science? Pure Science Answers questions about phenomena and mechanisms in the natural world. Why do you do it? Because we wanted to know! EX. Studying the ICE MAN Applied Science Application of scientific knowledge to practical problems. To fight disease, identify criminals, learn how to store hazardous wastes…etc.

What are the variables of an experiment? Smithers thinks 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, they're 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, Smithers counts how many stacks of papers each group has made. Group A made 1,587 stacks, Group B made 2,113 stacks. Independent Variable Special juice Dependent Variable How many stacks are made Control No special juice given (normal group) Constant 50 workers in each group.

What is an experimental control? Lisa is working on a science project. Her task is to answer the question: "Does Rogooti (which is a commercial hair product) affect the speed of hair growth". Her family is willing to volunteer for the experiment. Set up an experiment to test this. What would the independent variable be? Whether a family member gets Rogooti or not. What would the dependent variable be? Hair growth What would the control be? The family members that do NOT get Rogooti Is there a constant? No.

The conclusion What should Lisa conclude? Lisa is working on a science project. Her task is to answer the question: "Does Rogooti (which is a commercial hair product) affect the speed of hair growth". Her family is willing to volunteer for the experiment. Marge and Homer used Rogooti and grew 14 inches of hair in two weeks. An inch a day. Maggie and Bart did NOT use Rogooti and grew 2 cm of hair in two weeks. What should Lisa conclude? How would she represent this information?

Review