scientific method
DESCRIPTION
Experimental Design CourseTRANSCRIPT
EXPERIMENTAL DESIGNEXPERIMENTAL DESIGN
SCIENTIFIC METHODSCIENTIFIC METHOD
3rd Lecture
Dr. Sanaa Abd Eltawab 1 & Dr. Rasha Aly Elsayed 2
1 Beni Suef University 2 Al Azhar University
Intended learning outcomes
How Scientists Work: How Scientists Work: Solving the ProblemsSolving the Problems
Definition of Scientific Method Definition of Scientific Method Overview & Listing the Scientific Overview & Listing the Scientific
MethodMethod StepsSteps Scientific Method ExampleScientific Method Example - - Observing - QuestioningObserving - Questioning - Researching - Hypothesizing- Researching - Hypothesizing - Experimentation - Collect and record data- Experimentation - Collect and record data - Analyzing data - Draw conclusions- Analyzing data - Draw conclusions - Determine limitations- Determine limitations - Publish results- Publish results - Repeat Experiment- Repeat Experiment
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How Scientists Work: How Scientists Work: Solving the ProblemsSolving the Problems
Much of biology deals with solving problems These problems can be environmental,
ecological, health related, etc. No matter what types of problems
are being studied, scientists use the same problem-solving steps called the Scientific Method
The scientific method, is the most powerful tool yet devised for the analysis and solution of problems in the natural world.
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Scientific Method: Scientific Method: DefinitionDefinition
Scientific method is a body of techniques for investigating phenomena and acquiring new knowledge, as well as for correcting and integrating previous knowledge. It is based on gathering observable, empirical and measurable evidence subject to specific principles of reasoning, the collection of data through observation and experimentation, and the formulation and testing of hypotheses.
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Scientific Method:Scientific Method: Listing the StepsListing the Steps
Make an Observation Define the Problem Research the Problem State the Hypothesis Experiment to test Hypothesis Collect and Record Data Analyze Data Draw Conclusions Determine Limitations Report Results If needed, Do more investigation
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Then
And
QuestionQuestion
ResearchResearch
HypothesisHypothesis
Procedure/Method
Procedure/Method
DataData
ObservationsObservations
ConclusionConclusion
What does the scientist wantto learn more about?
Gathering of information
An “Educated” guess of ananswer to the question
Written and carefullyfollowed step-by-step
experiment designed to testthe hypothesis
Information collected duringthe experiment
Written description of whatwas noticed during the
experiment
Was the hypothesis correct or incorrect?
Next
Then
Next
And
Finally
First
S S
C C
I I E E
N N
T T
IIFFIICC
MM
EE
TT
HH
OO
DD
OO
VV
EE
RR
VV
II
EE
WW
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Scientific MethodScientific Method
Let’s break each of these steps down into their
individual components:
Ask Question
Do BackgroundResearch
ConstructHypothesis
Test with anExperiment
Analyze ResultsDraw Conclusion
Think!Try Again
Report Results
Hypothesis is True Hypothesis is Falseor Partially True
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Example for Scientific MethodExample for Scientific Method
Example: the Scientific Method using Redi’s Experiment on Spontaneous Generation
He was trying to disprove the idea of spontaneousGeneration (or actually that flies came from maggots, which came from flies)
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1. Observing1. Observing
Redi wanted to show what caused the appearance of maggots (and then flies) on meat
Make an observation
See something unusual
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2. Questioning2. Questioning
Recognize, state or define the problem Must be in the form of a question The obvious question is:
What’s the source of these worms?
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Belief based on prior Belief based on prior observationsobservations
Redi observed that maggots appeared on meat a few days after flies were on meat
No microscope = no way to see eggs But Redi believed that maggots came
from eggs that were laid by flies
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3.3. Researching
Gather information related to the problem
Read, observe, measure, take samples, etc.
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4. Hypothesizing 4. Hypothesizing
A hypothesis is: An educated guess, trial answer, possible
solution, prediction Must be a statement Must be testable or measurable Is based on your research and previous
experience
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Forming a HypothesisForming a Hypothesis
Redi’s Hypothesis: Flies produce maggots.
How could he test this? Through a controlled experiment
Predict a possible answer to the problem or question.
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5-Redi’s Controlled Experiment5-Redi’s Controlled Experiment
Redi used two groups of jars Jars that contained meat and no cover Jars that contained meat and gauze cover
Jars with meat
Uncovered jars
Covered jars
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Control and Experimental GroupsControl and Experimental Groups
used as a standard of comparison
the group containing the factor (variable) that has been changed
Uncovered jars
Covered jars
Two groups of jars
Control group: Control group:
Experimental group:Experimental group:
(manipulated or independent variable)(manipulated or independent variable)
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Variables in an ExperimentVariables in an Experiment
Variables - Factors that can be changed
what a scientist wants to observe
Controlled Variables- all the variables that remain constant
Manipulated Variable – (also called the Independent Variable) - factor in an experiment that a scientist purposely changes
Responding Variable-
(also called the Dependent Variable) - the outcome or results, factor in an experiment that may change because of the manipulated variable
Variables
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Setting up a Controlled ExperimentSetting up a Controlled Experiment
In a controlled experiment, only one factor is changed at a time. Independent variable: the
factor that is deliberately changed Dependent variable: the factor that the scientist wants to
observe; it changes in response to the independent variable
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Variables in Redi’s ExperimentVariables in Redi’s Experiment
Controlled Variables: jars, type of meat, location, temperature, time
Manipulated Variables: gauze covering that keeps flies away from meat
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Let’s think about this.…Let’s think about this.…
Which is the control group?
Which is the experimental group?
Two groups of Jars with meat
Uncovered jars
Covered jars
Covered jars
Uncovered jars
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OBSERVATIONS: Flies land on meat that is left uncovered. Later, maggots appear on the meat.
HYPOTHESIS: Flies produce maggots.
PROCEDURE
Manipulated Variables:gauze covering thatkeeps flies away from meat
Uncovered jars Covered jars
Several days pass
Maggots appear No maggots appear
Responding Variable: whether maggots appear
CONCLUSION: Maggots form only when flies come in contact with meat. Spontaneous generation of maggots did not occur.
Controlled Variables:jars, type of meat,location, temperature,time
Redi’s Experiment on Spontaneous GenerationRedi’s Experiment on Spontaneous Generation
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6. Collect and Record Data6. Collect and Record Data
Types of Recorded Data
Quantitative - observations that involve measurements/numbers; i.e. 3 days, 12 maggots, 4 g, 13 sec, 8 liters
Qualitative - observations thatdo not involve numbers, are of a descriptive naturei.e. white maggots covered the meat, leaves were all wilting
observations and measurementsmade in an experiment
DataData::
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7. Analyze the Data7. Analyze the Data
Examine data tables, charts, and graphs Examine experimental notes Look for trends, patterns, and averages What does the data show Put your data into words
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8. Draw Conclusions8. Draw Conclusions
Restate the hypothesis:Example: Flies produce maggots.
Accept or reject the hypothesis. Support your conclusion with specific, numerical data. What was Redi’s conclusion?
Flies lay eggs too small to be seen. Maggots found on rotting meat are produced
from the eggs laid by flies. Maggots are not appearing due to
spontaneous generation!
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9. Determine Limitations9. Determine Limitations
Scientists look for possible flaws in their research.
They look for faulty (inaccurate) data.
They look for experimental error or bias's.
They decide on the validity of their results.
They make suggestions for improvement or raise new questions.
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10. Publish Results 10. Publish Results
Communication is an essential part of science
Scientists report their results in journals, on the internet, or at conferences
This allows their experiments to be evaluated and repeated
Scientists can build on previous work of other scientists
Redi’s experimenton insects generation
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Repeating the InvestigationRepeating the Investigation
Sometimes results are unexpected.
John Needham challenged Redi’s experiment and designed his own to show that spontaneous generation CAN occur under certain circumstances.
Lazzaro Spallanzini designed a slightly different experiment to improve on Needham’s work
Repeat the Repeat the experiment!experiment!
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Repeating the ExperimentRepeating the Experiment(continued)
Louis Pasteur further modified the experiment.
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Thank YouThank You30