S TEPS IN THE S CIENTIFIC M ETHOD Observation Hypothesis Experiment Data Collection Conclusion Retest
O BSERVATIONS Gathered through your senses. A scientist notices something in the natural world. Repeated observations over a long period of time.
O BSERVATIONS An example of an observation might be that young dolphins and small porpoises with horrific injuries continually show up on the shores of Virginia and Scottland’s East coast.
H YPOTHESIS A suggested solution to a problem. Must be testable. Written as an “If…then…” statement. Predicts an outcome.
H YPOTHESIS A hypothesis might be that the mammals had died through 'blast trauma'. In American cases, this was supposedly from exercises by the US Navy, and in Scotland from air guns used by oil rig technicians to detect undersea caverns.
E XPERIMENT A procedure to test the hypothesis. Can be an experiment, model, or observation. The hypothesis was dismissed after further examination of the mammals' bodies revealed the injuries - broken ribs, imploding lungs, damaged livers and massive internal bleeding - could only have come from prolonged, focused attacks. When tell-tale teeth-marks were identified, the dolphin - the mammal classified as one of the world's most intelligent, sensitive and sociable creatures - became the official suspect. Confirmation of the murders came by way of two shocking films shot by holidaymakers.
A G OOD E XPERIMENT Will be repeatable. Change only one variable at a time. Will have a large sample size.
S CIENTIFIC E XPERIMENTS F OLLOW R ULES An experimenter changes one factor and observes or measures what happens.
V ARIABLES Variable Factor in the experiment that is being tested.
I NDEPENDENT V ARIABLE 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
D EPENDENT V ARIABLE The factor that is measured or observed is called the dependent variable. Observed and measured during the experiment Graphed on the Y-AXIS
G RAPHING V ARIABLES The independent variable would be the temperature. The dependent variable is the metabolic rate.
C ONSTANTS The experimenter makes a special effort to keep other factors constant so that they will not effect the outcome. Susie want to know how different colors of light effect the growth of plants. She buys 5 ferns of the same species, which are all approximately the same age and height. She places one in white light, one in blue light, one in green light, one in red light, and one in a closet. All of the ferns are planted in Miracle Grow and given 20 mL of water a day for two weeks. After the two weeks, Susie observes the plants and takes measurements. In this experiment, the species, age, original height, the soil and amount of water are ALL constants.
C ONTROLS Establish a “status quo” How conditions are under normal circumstances. Controls are NOT being tested. Controls are used for COMPARISON
E XAMPLE … Susie want to know how different colors of light effect the growth of plants. She buys 5 ferns of the same species, which are all approximately the same age and height. She places one in white light, one in blue light, one in green light, one in red light, and one in a closet. All of the ferns are planted in Miracle Grow and given 20 mL of water a day for two weeks. After the two weeks, Susie observes the plants and takes measurements.
V ARIABLES IN THIS EXPERIMENT … Variations in the light color are the independent variables Growth in the plants are the dependent variables Having the same species at the same age, starting out at the same height, using the same soil and amount of water are all constants. The plant that was placed in the closet is the control.
W HY DO SCIENTISTS REPEAT EXPERIMENTS ? In order to verify results, experiments must be RETESTED! It adds validity to the findings.
V ALID E XPERIMENTS Two groups are required --- the control & experimental groups There should be only one variable each experiment
D ATA Results of the experiment May be quantitative (numbers) or qualitative (descriptive)
D ATA Must be organized Can be organized into charts, tables, or graphs
T RENDS IN D ATA 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.
C ONCLUSION The answer to the hypothesis based on the data obtained from the experiment
H OW DO SCIENTISTS COMMUNICATE FINDINGS ? When scientists want to communicate the results of their experiment, they use SCIENTIFIC JOURNALS or other publications!
P URE AND A PPLIED S CIENCE 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 dolphin deaths Applied Science Application of scientific knowledge to practical problems. Why do you do it? To fight disease, identify criminals, learn how to store hazardous wastes…etc.
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