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The Scientific Method
Transcript of The Scientific Method
Ask a Question
What is the current understanding?
Analyze the results
Crunch the numbers
Was the hypothesis supported?
May actually be observed with our senses
Plants, animals, rivers, mountains, oceans,
planets, and others.
Cannot be directly observed with our senses.
Requires the use of machines to help us detect and measure them or by observing their effects on other things.
Tiny particles, forces (like gravity), radiation, events that happened long ago, processes that take very long periods of time, etc.
"I wonder why that is?"
Form a hypothesis
What is a hypothesis?
A testable explanation or prediction
A biologist notices that she has seen fewer song birds this spring than she has in previous years. She makes some formal observations and confirms that the number of birds in the area has declined.
She wants to develop a hypothesis.
What might her hypothesis be?
The birds or their young are being eaten by new predators in the area.
The birds have migrated to a different area.
A new source of pollution such as a factory or farming operation is affecting the bird populations.
The birds are being affected by a new disease.
All of these are testable explanations.
Design an experiment!
Experiments are controlled
Variables are things that can affect the results of an experiment.
A good experiment tests the effects of just one variable.
The effects of other variables should be minimized or accounted for.
An experiment is a procedure that tests a hypothesis.
By the end of the experiment, you will know whether or not your hypothesis is supported or not supported.
In an experiment, there should be one group that isn't being experimented on. This is the control group.
What purpose does this serve?
Experimental groups are the subjects in the experiment that are being experimented upon.
Independent Variable: The thing the scientist changes to affect the experimental groups.
Dependent Variable: The thing that changes BECAUSE of the experiment.
Demonstration Time ...
Ethics in Science
Experiments should not do unnecessary harm.
Scientists should have the consent of people participating in the experiment.
Scientists must report results honestly.
If a scientist falsely claims to have developed a new treatment for a disease, that could affect how people with that disease behave and they could be put in danger.
Other scientists must be able to replicate the experiment to verify the results.
Scientists should not be influenced by groups who have an interest in his results.
Study without Experiments
Sometimes an experiment is not possible or ethical.
Scientists make observations, sometimes over long periods of time, to try to see trends that show relationships between the things they are investigating.
This sort of investigation is called a study.
Draw conclusions ...
When we use our data to draw logical conclusions, we are making
. Our conclusions should be the best explanation for the data that we can come up with.
The conclusions could be verified or refuted by repeating the experiment or study.
Beware of Bias
All humans have particular attitudes, interests, and points of view. These are potential sources of bias.
Scientists have to be very careful not to let their biases affect their experiments or conclusions.
If the results of an experiment are biased, further experiments and studies may disprove its conclusions.
A general explanation for a lot of data
Well supported by evidence
Consistent with other theories
May be adapted to accept new evidence
Few assumptions (Occam's Razor)
Becoming a theory is as good as it gets!
Theory of Evolution
Big Bang Theory
Theory of Plate Tectonics
Theories do NOT graduate to become laws.
Laws are observations or mathematical relationships that are (apparently) always true, everywhere in the universe.
Theories are explanations for those observations.
Before a paper is published, it must be peer reviewed. It is checked by other scientists; experts in the same field of study.
They make sure the experiment was well designed and properly carried out and that the conclusion is based on the results.
New findings are written up in papers and published in science journals.
Scientists read these journals to keep up with current findings in fields they are interested in.
A scientist might try to repeat an experiment described in a journal to see if they can replicate the results.
Law of Gravity
Newton's Laws of Motion
Conservation of Mass and Energy
Laws of Thermodynamics
Qualitative vs. Quantitative
Information that we obtain using observation is called
Data may be
Quantitative data is in the form of a quantity. It is the result of direct and objective measurement.
Ex: The car weighs 900 kg.
The leaf is 7 cm long.
The swimming pool has a volume of 10,000 liters.
Qualitative data describe the qualities of something. It is descriptive and less precise than quantitative data.
Ex: The sandwich was tangy.
The flowers were yellow.
The lion was aggressive.