scientific method

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EXPERIMENTAL DESIGN EXPERIMENTAL DESIGN SCIENTIFIC METHOD SCIENTIFIC METHOD 3 rd Lecture Dr. Sanaa Abd Eltawab 1 & Dr. Rasha Aly Elsayed 2 1 Beni Suef University 2 Al Azhar University

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Experimental Design Course

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Page 1: Scientific method

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

Page 2: Scientific method

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