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Scientific methodpowerpoint
- 1. Copyright © 2009 Pearson Education, Inc.
© 2013 Pearson Education, Inc.
PowerPoint Lecture prepared by
Jill Feinstein
Richland Community College
Fourth Edition
BIOLOGYScience for Life | with Physiology
Colleen Belk • Virginia Borden Maier
ChapterChapter 11
Can Science Cure the Common Cold?
Introduction to the Scientific Method
* Components of this PowerPoint were altered by Lissa Walls to better fit
the learning objectives of Integrated Science: The Living World (SCI 106)
*
- 2. © 2013 Pearson Education, Inc.
1.1 The Process of Science
Science refers to a body of knowledge
Science is not a giant collection of facts to be
memorized.
It is important to learn about the process of science
called the scientific method.
The scientific method is used to solve problems
and answer questions.
Observations
Proposing ideas
Testing ideas
Discarding or modifying ideas based on results
- 3. © 2013 Pearson Education, Inc.
1.1 The Process of Science
The Nature of Hypotheses
Hypothesis: proposed explanation for a set of
observations
Scientific Hypotheses need to be:
Testable –possible to examine the hypothesis through
observations
Falsifiable –able to be
proven false if it is untrue
Objective – not influenced by personal feelings or
opinions
Ethical - moral
- 4. © 2013 Pearson Education, Inc.
1.1 The Process of Science
Where do hypotheses come from?
Both logical and creative influences are used to
develop a hypothesis
- 5. © 2013 Pearson Education, Inc.
1.1 The Process of Science
Scientific Theory
Powerful, broad explanation of a large set of
observations
Based on well supported hypotheses
Supported by research from several different
independent sources
- 6. © 2013 Pearson Education, Inc.
1.1 The Process of Science
Steps of the Scientific
Method
The process looks
something like this:
- 8. © 2013 Pearson Education, Inc.
1.1 The Process of Science
The Logic of Hypothesis Tests
A hypothesis that fails our test is rejected and
considered disproven.
A hypothesis that passes is supported, but not
proven.
Why not? An alternative hypothesis might be
the real explanation.
- 9. © 2013 Pearson Education, Inc.
1.2 Hypothesis Testing
The Experimental Method
Experiments are designed to test specific
hypotheses.
Variables: factors that can change in value under
different conditions
Independent variables can be manipulated by
the scientist
Dependent variables cannot be changed by
the researcher
Standardized variables (aka controlled
variables) kept constant so that any difference in
outcome is due ONLY to treatment
- 10. © 2013 Pearson Education, Inc.
1.2 Hypothesis Testing
Controlled Experiments
Controlled experiment: tests the effect of a
single variable
Control: a subject (or group) who is not exposed
to the experimental treatment but has all other
variables the same
Given either no treatment or a placebo
- 11. © 2013 Pearson Education, Inc.
1.2 Hypothesis Testing
Controlled Experiments
Differences seen between the experimental
group and control group can be attributed to
the experimental treatment
Random Assignment
An effective way of assigning individuals to
groups for testing
- 12. © 2013 Pearson Education, Inc.
1.2 Hypothesis Testing
Controlled Experiments
Example: Echinacea tea experiment:
Hypothesis: drinking Echinacea tea relieves
cold symptoms
Experimental group drinks Echinacea tea 5-6
times daily
Control group drinks “sham” Echinacea tea 5-6
times daily (placebo)
Both groups rated the effectiveness of their
treatment on relieving cold symptoms
- 13. © 2013 Pearson Education, Inc.
1.2 Hypothesis Testing
Controlled Experiments
People who received
echinacea tea felt that
it was 33% more effective
at reducing symptoms
- 14. © 2013 Pearson Education, Inc.
1.2 Hypothesis Testing
Minimizing Bias in Experimental Design
If human subjects know whether they have received
the real treatment or a placebo, they may be biased.
Blind experiment: subjects do not know what kind
of treatment they have received
Double blind experiment: the person
administering the treatments and the subjects do
not know who is in each group until after the
experiment is over
- 15. © 2013 Pearson Education, Inc.
1.2 Hypothesis Testing
Minimizing Bias in Experimental Design
- 16. © 2013 Pearson Education, Inc.
1.2 Hypothesis Testing
The “gold standard” for experimentation
Double-blind, placebo controlled, and randomized
experiments
Model systems can be used in experiments
when it appears too dangerous or unethical to test
on humans
examples: mice, rats, dogs and pigs
A correlation can be used to test hypotheses
when controlled experiments on humans are
impossible to perform
- 17. © 2013 Pearson Education, Inc.
1.2 Hypothesis Testing
Using Correlation to Test Hypotheses
Using existing data, is there a correlation
between variables?
Hypothesis: stress makes people more susceptible
to catching a cold
Is there a correlation between stress and the
number of colds people have caught?
- 18. © 2013 Pearson Education, Inc.
1.2 Hypothesis Testing
Using Correlation to Test Hypotheses
Results of such a study: the number of colds
increases as stress levels increase
Caution! Correlation does not imply causation!!
- 19. © 2013 Pearson Education, Inc.
1.2 Hypothesis Testing
Using Correlation to Test Hypotheses
The correlation might be due to other reasons
- 20. © 2013 Pearson Education, Inc.
1.3 Understanding Statistics
Overview: What Statistical Tests Can Tell Us
Data collected during experimentation should be
organized and analyzed using statistical methods
Comparing means (averages) is a common way to
compare the data from two groups
Statistical tests will tell us if differences between
groups are due to treatment or due to chance
Statistically significant: unlikely the observed
difference is due to chance IF experiment was
designed and carried out properly
AKA there is a true difference between the two
groups/items compared
- 21. © 2013 Pearson Education, Inc.
1.3 Understanding Statistics
The Problem of Error
During experimentation researchers need to minimize error;
errors affect the outcome of experiments
Experimental error: inconsistent or incorrect
measurements, poorly functioning equipment, timing errors,
confusing instructions to subjects, etc.
Sampling error: estimation error because of surveying a
sample of the population rather than the whole population
Sample size: the number of units (people, plants,
animals, illnesses) to be tested/surveyed in an
experiment
A larger sample size is more true of the population from
which the sample was taken
- 22. © 2013 Pearson Education, Inc.
1.3 Understanding Statistics
What Statistical Tests Cannot Tell Us
If an experiment was designed and carried out
properly
If observer error occurred; statistical tests can only
evaluate the probability of sampling error
Practical or biological significance of results
- 23. © 2013 Pearson Education, Inc.
1.4 Evaluating Scientific Information
Primary Sources
Researchers can submit a paper about their
experimental methods and results to a professional
journal (primary source)
Primary Sources undergo peer review: evaluation
of submitted papers by other experts
Secondary sources: books, news reports, the
internet, and advertisements
- 24. © 2013 Pearson Education, Inc.
1.4 Evaluating Scientific Information
Information from Anecdotes
Anecdotal evidence is based on one person’s
experience, not on experimental data
Example: a testimonial from a celebrity
- 25. © 2013 Pearson Education, Inc.
1.4 Evaluating Scientific Information
Science in the News
- 26. © 2013 Pearson Education, Inc.
1.4 Evaluating Scientific Information
Science in the News
Secondary sources may be missing critical
information or report the information incorrectly
Consider the source of media reports
Be careful with the Internet since anyone can
post information
Be very cautious about claims made in paid
advertisements
- 27. © 2013 Pearson Education, Inc.
1.4 Evaluating Scientific Information
Understanding Science from Secondary Sources
Use your understanding of the scientific method to
evaluate findings stated by secondary sources
News media generally highlight only those science
stories that seem newsworthy
They are more likely to report a positive result than
a negative one
- 28. © 2013 Pearson Education, Inc.
1.5 Is There a Cure for the Common Cold?
No, but prevention methods are known
Wash your hands!
No effect on cold susceptibility:
Vitamin C
Exposure to cold temperatures
Exercise
No vaccine for the common cold