Scientific Methods
001b
The nature of science• Science:
– A systematic process for learning about the world and testing our understanding of it
– The accumulated body of knowledge that results from a dynamic process of observation, testing, and discovery
• Science is essential:– To sort fact from fiction – Develop solutions to the problems we face
Pure Science- pursuit of knowledge
Applied Science- search for practical uses of scientific knowledge
tetradoxin
Pain relief in terminal cancer patients
Discovery or observational science.
Hypothesis-driven or experimental science.
Two Primary Approaches to Science
Scientists test ideas
Hypothesis-Driven Studies
Discovery/Observational Studies
Science is empirical. It relies on observation and experience.
The phenomenon studied must be measurable.
Phenomenon that cannot be measured:Is this painting beautiful?Does God exist?
It must be consistent with known natural laws and well-established, well-documented existing theories.
It must be derived objectively from independently confirmable observations.
All scientific knowledge must be regarded as tentative.
Characteristics of Scientific Explanations
Hypothesis: Hermatypic corals exposed to temperatures above 36oC expel their symbiotic zoothanthellae.
Hypothesis: Naval explosions at the thermocline layer cause hearing loss in whales.
Hypothesis:Ulua are better predators.
Scientific statements must be testable and reproducible (i.e., valid & reliable).
Hypothesis:The fibropapilloma virus causes tumors in green sea turtles.
Some Scientific Questions Can’t Be Answered By Experimentation
Discovery or observational science is still science; falsifiable hypotheses based on natural phenomenon are proposed to best account for observations.
The Scope and Limitations of Science
• Science acquires knowledge through examination of falsifiable hypotheses based on natural phenomena.
• This sets a limit on science; science cannot speak directly to such issues as morality or religion.
• The domain and limit of science are often misunderstood.
Scientific Method
A way to answer questions
Must be testable & repeatable, i.e., validity and reliability
Deductive Reasoning- general to specificreasoning from general theories to account for specific experimental results
(theory-data collection-analysis)
Inductive Reasoning- specific to generalreasoning from specific observations and experiments to more general theories (data collection-analysis-theory)
January1992 in the North Pacific
Rubber Duckies and Ocean currents.
• Jim Ingram (NOAA scientist)- offered a reward
• He graphed and studied the data as it came in.
• Hypothesis: ocean currents were moving the ducks in about the same speed and direction that the currents were going!
Toy trekResearchers expect some 29,000 bath toys lost at sea in 1992 to make the ice-covered trek over the North Pole and to the North Atlantic by this summer.
The scientific method
• Observations
• Question
• Formulate Hypothesis
• Conduct Experiment
• Analyze Results
• Conclusions
• Discussion
A technique for testing ideas
Testing predictions• Experiment: an activity that tests the validity of a
hypothesis• Variables: conditions that can be manipulated
and/or measured– Independent variable: a condition that is manipulated– Dependent variable: a variable that is affected by the
manipulation of the independent variable
• Controlled experiment: one in which all variables are controlled– Control: the unmanipulated point of comparison– Treatment: the manipulated point of comparison
• Data: information that is generally quantitative (numerical)
Experiments test the validity of a hypothesis
• Manipulative experiments yield the strongest evidence– Provides the strongest type of evidence– Reveal causal relationships: changes in independent
variables cause changes in dependent variables– But many things can’t be manipulated: long-term or
large-scale questions (i.e., global climate change)
• Natural experiments show real-world complexity– Only feasible approach for ecosystem or planet-scale– Results are not so neat and clean, so answers aren’t
simply black and white
Testing predictions• Experiment: an activity that tests the validity of a
hypothesis• Variables: conditions that can be manipulated
and/or measured– Independent variable: a condition that is manipulated– Dependent variable: a variable that is affected by the
manipulation of the independent variable
• Controlled experiment: one in which all variables are controlled– Control: the unmanipulated point of comparison– Treatment: the manipulated point of comparison
• Data: information that is generally quantitative (numerical)
Experiments test the validity of a hypothesis
• Manipulative experiments yield the strongest evidence– Provides the strongest type of evidence– Reveal causal relationships: changes in independent
variables cause changes in dependent variables– But many things can’t be manipulated: long-term or
large-scale questions (i.e., global climate change)
• Natural experiments show real-world complexity– Only feasible approach for ecosystem or planet-scale– Results are not so neat and clean, so answers aren’t
simply black and white
Observation:
Question:
Hypothesis:
Test hypothesis:
Analyze Results:
Draw Conclusion:
Ben Franklin & the Gulf Stream
1996
1786
Coral Mapping (Molokai)
Mangrove Study
Do sponges affect mangrove root growth?
Select a large sample size
Randomly divide the sample into 2 groups
Treat the groups equally in all ways but one
Observe or make measurements
Compare results
Mangrove Study
Pisaster
Paine’s study on Pisaster and blue mussels
What effect does starfish removal have on community structure?
chiton limpet
mussels (Mytilus)
barnacles
Keystone Species
Paine’s study on Pisaster and blue mussels
What is difference between hypothesis, theory & law?
Hypothesis - “an educated guess”; a tentative explanation of phenomena.
Theory - a widely accepted explanation of natural phenomena; has stood up to
thorough & continual testing.
Law - a statement of what always occurs under certain conditions.
Theories
Evolution
Cell Theory
Laws
Biology: Mendelian Inheritance
Physics, Chemistry, Math- Lots!!!!
The Blind Men and the Elephant (Saxe; 1816-1887)
I.It was six men of Indostan
To learn much inclined,Who went to see the elephant
(Though all of them were blind), That each by observationMight satisfy their mind.
II.The First approached the elephant,
And happened to fallAgainst his broad sturdy side,
At once began to bawl:“Bless me!—but the Elephant is very like a wall!”
III.The Second, feeling of the tusk ,Cried, “Ho!—what have we here
So very round and smooth and sharp?To me ‘t is mighty clear
This wonder of an ElephantIs very like a spear!”
IV.The Third approached the animal,
And happening to takeThe squirming trunk within his hands,
Thus boldly up and spake:“I see,” quoth he, “the Elephant
Is very like a snake!”
V.The Fourth reached out his eager hand,
And felt about the knee.“What most this wondrous beast is like
Is might plain’” quoth he;“‘T is clear enough the Elephant
Is very like a tree!”
VI.The Fifth, who chanced to touch the ear,
Said, “E’en the blindest manCan tell what this resembles most;
Deny the fact who can,This marvel of an Elephant
Is very like a fan!”
VII.The Sixth no sooner had begun
About the beast to grope,Than seizing on the swinging tail
That fell within his scope,“I see,” quoth he, “the Elephant
Is very like a rope!”
VIII.And so these men of Indostan
Disputed loud and long,Each with his own opinionExceeding stiff and strong,
Though each was partly in the right,And all were in the wrong!
Moral.
So, oft in these theological wars
The disputants, I ween,
Rail on in utter ignorance
Of what each other mean,
And prate about an elephant
Not one of them has seen!
The Blind Men and the Elephant, Part 2,
I.They talked, those men from Indostan
While standing at the door,Of elephants and how they looked
(This talk was such a bore!),At last they agreed that the knowledge gained
Required something more.
II.Perhaps each one in his own way,
Did learn a bitOf the beast’s elusive mystery,
But just a part of itWith work, they thought, that they might see
The puzzle pieces fit.
III.‘Twas obvious to all of them
For learning to progress,That they must share in what they found—
Jointly sort out the mess.And seek to fully understand
Elephants, more or less.
IV.Some worked alone and some in teams,
In both the field and lab.Models were made: some soft, some hard
Some good, some pretty bad.But when they pooled the useful work,
And truth they made a grab.
V.They checked each other’s methods out,
Some kept, some put asunder.To use the ones which passed the test
Reduced the chance of blunder.Then they’d trust what they had learned
Of elephants’ fine wonders.
VI.They made great strides in what they knew
Of the nature of the beast.Of what and where and how and why
They knew much more at least.For blind men learned how best to learn
And vision soon increased!
Inquiry1. What is the difference between a
hypothesis, theory and law?2. Can a theory ever be proven?3. In the mangrove study, what is the
dependant variable?4. State Ben Franklin’s hypothesis.5. In Paine’s study on Pisaster, what role
did blue mussels play?
QUESTION: Review
Which is the correct order of the scientific method?
a) Observation, hypothesis, testing, resultsb) Hypothesis, observation, testing, resultsc) Observation, testing, results, hypothesisd) observation, testing, hypothesis, results
QUESTION: Interpreting Graphs and Data
What happens if test results reject a hypothesis?
a) The scientist formulates a new hypothesis.
b) It shows the test failed.c) The scientist should be
fired.d) The scientist used faulty
data .