How Scientists How Scientists WorkWork
How do scientists test How do scientists test hypotheses? hypotheses?
How does a scientific How does a scientific theory develop?theory develop?
InquiryInquiry Inquiry Inquiry is the search for information is the search for information
and explanationand explanation Scientists begin an inquiry Scientists begin an inquiry
investigation with a questioninvestigation with a question There are two main types of scientific There are two main types of scientific
inquiry: discovery science and inquiry: discovery science and hypothesis-based sciencehypothesis-based science
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Discovery ScienceDiscovery Science Discovery science Discovery science describes natural describes natural
structures and processesstructures and processes This approach is based on observation This approach is based on observation
and the analysis of dataand the analysis of data
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Types of DataTypes of Data Data Data are recorded observations or are recorded observations or
items of informationitems of information Data fall into two categoriesData fall into two categories
QualitativeQualitative, or descriptions rather than , or descriptions rather than measurementsmeasurements
QuantitativeQuantitative, or recorded , or recorded measurements, which are sometimes measurements, which are sometimes organized into tables and graphsorganized into tables and graphs
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Fig. 1-23
Induction in Discovery Induction in Discovery ScienceScience
Inductive reasoning Inductive reasoning draws draws conclusions through the logical conclusions through the logical process of inductionprocess of induction
Repeat specific observations can lead Repeat specific observations can lead to important generalizationsto important generalizations For example, For example, ““the sun always rises in the the sun always rises in the
easteast””
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Deduction: The Deduction: The ““If…ThenIf…Then”” Logic of Logic of Hypothesis Based ScienceHypothesis Based Science
Deductive reasoning Deductive reasoning uses general uses general premises to make specific predictionspremises to make specific predictions
For example, For example, ifif organisms are made of organisms are made of cells (premise 1), and humans are cells (premise 1), and humans are organisms (premise 2), organisms (premise 2), then then humans humans are composed of cells (deductive are composed of cells (deductive prediction)prediction)
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A Closer Look at Hypotheses in A Closer Look at Hypotheses in Scientific InquiryScientific Inquiry
A hypothesis must be A hypothesis must be testable testable and and falsifiablefalsifiable
Hypothesis-based science often makes Hypothesis-based science often makes use of two or more alternative use of two or more alternative hypotheseshypotheses
Failure to falsify a hypothesis does not Failure to falsify a hypothesis does not prove prove that hypothesisthat hypothesis For example, you replace your flashlight For example, you replace your flashlight
bulb, and it now works; this supports the bulb, and it now works; this supports the hypothesis that your bulb was burnt out, hypothesis that your bulb was burnt out, but does not prove it (perhaps the first but does not prove it (perhaps the first bulb was inserted incorrectly)bulb was inserted incorrectly)Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Myth of the Scientific The Myth of the Scientific MethodMethod
The The scientific method scientific method is an idealized is an idealized process of inquiryprocess of inquiry
Hypothesis-based science is based on Hypothesis-based science is based on the the ““textbooktextbook”” scientific method but scientific method but rarely follows all the ordered stepsrarely follows all the ordered steps
Discovery science has made important Discovery science has made important contributions with very little contributions with very little dependence on the so-called scientific dependence on the so-called scientific methodmethod
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Scientific MethodScientific MethodStating the ProblemStating the Problem
How do new living things, or How do new living things, or organisms, come into being? organisms, come into being?
Forming a HypothesisForming a Hypothesis Francesco Redi questioned the Francesco Redi questioned the theory of spontaneous theory of spontaneous generationgeneration
flies produce maggotsflies produce maggots
Scientific MethodScientific MethodSetting Up a Controlled Setting Up a Controlled ExperimentExperiment
Recording and Analyzing Recording and Analyzing ResultsResults
Drawing a ConclusionDrawing a Conclusion Publishing and Repeating Publishing and Repeating InvestigationsInvestigations
Setting Up a Controlled Setting Up a Controlled ExperimentExperiment
VariablesVariables - factors in an - factors in an experiment that can change experiment that can change equipment used, type of material, equipment used, type of material, amount of material, temperature, amount of material, temperature, light, and timelight, and time
Only one variable tested at a Only one variable tested at a timetime
All other variables are kept All other variables are kept unchanged, or unchanged, or controlledcontrolled. . controlled experimentcontrolled experiment. .
Types of variablesTypes of variables Independent variableIndependent variable
Manipulated variableManipulated variableWhat you changeWhat you change
Dependent variableDependent variableResponding variable Responding variable Changes in response to Changes in response to manipulated variablemanipulated variable
What you measureWhat you measure
Publishing and Publishing and Repeating InvestigationsRepeating Investigations Needham’s Test of Redi’s Needham’s Test of Redi’s
FindingsFindings mid-1700s, John Needham, mid-1700s, John Needham, an English scientist an English scientist
attacked Redi’s work attacked Redi’s work claimed spontaneous claimed spontaneous generation could occur generation could occur under right conditions under right conditions
heated gravyheated gravy
Publishing and Publishing and Repeating InvestigationsRepeating Investigations
Spallanzani’s Test Spallanzani’s Test of Redi’s Findingsof Redi’s Findings Lazzaro Spallanzani, Lazzaro Spallanzani, ItalianItalian
Broth had not been Broth had not been boiled long enoughboiled long enough
Boiled a container of Boiled a container of broth in a water bath broth in a water bath for 45 minutesfor 45 minutes
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Publishing and Publishing and Repeating InvestigationsRepeating InvestigationsPasteur’s Test of Pasteur’s Test of Spontaneous Spontaneous GenerationGeneration In 1864, French In 1864, French scientist, Louis Pasteur scientist, Louis Pasteur
designed a flask with designed a flask with long curved neck long curved neck
showed all living things showed all living things come from other living come from other living things things Image from: http://www.chemheritage.org/EducationalServices/pharm/antibiot/readings/spogen.htm
VerifiableVerifiable What does this word mean?What does this word mean? How does it relate to science??How does it relate to science??
How a Theory How a Theory DevelopsDevelops
Hypothesis may become so well Hypothesis may become so well supported scientists consider it supported scientists consider it a a theorytheory. .
Theories enable scientists to make Theories enable scientists to make accurate predictions about new accurate predictions about new situationssituations
As new evidence is uncovered, a As new evidence is uncovered, a theory may be revised or replaced theory may be revised or replaced by a more useful explanationby a more useful explanation
Precision and AccuracyPrecision and Accuracy PrecisionPrecision
Describes the unit you used to measureDescribes the unit you used to measure The smaller the unit of measurement, The smaller the unit of measurement,
the more precise the measurementthe more precise the measurement AccuracyAccuracy
How close the measurement is to the How close the measurement is to the actual valueactual value
How different your number is from the How different your number is from the accepted valueaccepted value
Qualitative vs. Qualitative vs. quantitativequantitative
QualitativeQualitative Descriptive dataDescriptive data
QuantitativeQuantitative Measurement dataMeasurement data