1. EXPERIMENTAL DESIGN
SCIENTIFIC METHOD
Dr. Sanaa Abd Eltawab 1 & Dr. Rasha Aly Elsayed 2
1
Beni Suef University 2 Al Azhar University
3rd Lecture
2. Intended learning outcomes
2
How Scientists Work: Solving the Problems
Definition of Scientific Method
Overview & Listing the Scientific Method Steps
Scientific Method Example
- Observing - Questioning
- Researching - Hypothesizing
- Experimentation - Collect and record data
- Analyzing data - Draw conclusions
- Determine limitations
- Publish results
- Repeat Experiment
3. How Scientists Work: Solving the Problems
3
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.
4. Scientific Method: Definition
4
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.
5. Scientific Method: Listing the Steps
5
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
6. First What does the scientist want
Question to learn more about?
Then
6
Research Gathering of information
Next
S O An “Educated” guess of an
Hypothesis
C
answer to the question
M V Then
I
E
Written and carefully
E
Procedure/ followed step-by-step
Method experiment designed to test
the hypothesis
E T R Next
N H V Data
Information collected during
the experiment
O I And And
T
Written description of what
E Observations was noticed during the
I
D experiment
W
Finally
F Conclusion
Was the hypothesis correct
or incorrect?
I
7. Scientific Method
Ask Question
7
Do Background
Research
Construct Think!
Let’s break each Hypothesis Try Again
of these steps Test with an
down into their Experiment
individual Analyze Results
components: Draw Conclusion
Hypothesis is False
Hypothesis is True
or Partially True
Report Results
8. Example for Scientific Method
8
Example: the Scientific Method using Redi’s
Experiment on Spontaneous Generation
He was trying to disprove the idea of spontaneous
Generation (or actually that flies came from
maggots, which came from flies)
9. 1. Observing
9
Make an observation
See something unusual
Redi wanted to show
what caused the
appearance of maggots
(and then flies) on meat
10. 2. Questioning
10
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?
11. Belief based on prior
11
observations
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
13. 3.
13
Researching
Gather information related to the
problem
Read, observe, measure, take
samples, etc.
14. 4. Hypothesizing
14
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
15. Forming a Hypothesis
15
Predict a possible answer to the problem or question.
Redi’s Hypothesis:
Flies produce maggots.
How could he test this?
Through a controlled experiment
16. 5-Redi’s Controlled Experiment
16
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
17. Control and Experimental Groups
17
Control group: used as a standard of
comparison
Experimental group: the group containing the
factor (variable) that has been changed
(manipulated or independent variable)
Two groups
of jars
Uncovered
jars
Covered
jars
18. Variables in an Experiment
18
Variables - Factors that can be changed
Variables
Controlled Variables Manipulated Variable – Responding Variable-
- all the variables that (also called the
remain constant Independent Variable) - (also called the
factor in an experiment that Dependent Variable) - the
a scientist purposely outcome or results, factor in
changes an experiment that may
change because of the
manipulated variable
what a scientist wants to observe
19. Setting up a Controlled Experiment
19
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
20. Variables in Redi’s Experiment
20
Controlled Variables: jars, type of meat,
location, temperature, time
Manipulated Variables:
gauze covering
that keeps flies
away from meat
21. Let’s think about this.…
21
Which is the control group? Uncovered jars
Which is the experimental group?
Covered jars
Two groups of
Jars with meat
Uncovered
jars
Covered
jars
22. Redi’s Experiment on Spontaneous Generation
OBSERVATIONS: Flies land on meat that is left uncovered. Later, maggots appear on the meat.
HYPOTHESIS: Flies produce maggots.
22
PROCEDURE
Uncovered jars Covered jars
Controlled Variables:
jars, type of meat,
location, temperature,
time
Several
days pass
Manipulated Variables:
gauze covering that
keeps flies away from
meat
Responding Variable:
whether maggots
appear Maggots appear No maggots appear
CONCLUSION: Maggots form only when flies come in contact with meat. Spontaneous
generation of maggots did not occur.
23. 6. Collect and Record Data
23
20
Data: observations and measurements
made in an experiment
Types of Recorded Data
Quantitative - observations that
involve measurements/numbers;
i.e. 3 days, 12 maggots, 4 g, 13 sec,
8 liters
Qualitative - observations that
do not involve numbers, are of a
descriptive nature
i.e. white maggots covered the meat,
leaves were all wilting
24. 7. Analyze the Data
24
21
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
25. 8. Draw Conclusions
25
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!
26. 9. Determine Limitations
26
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.
27. 10. Publish Results
27
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
Redi’s experiment
on insects generation
work of other scientists
28. Repeating the Investigation
28
Sometimes results are unexpected.
Repeat the experiment!
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