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Chapter 1
Can Science Cure the Common Cold?
Introduction to the Scientific Method
Fourth Edition
BIOLOGY
Science for Life | with Physiology
Colleen Belk • Virginia Borden Maier
© 2013 Pearson Education, Inc.
Copyright © 2009 Pearson Education, Inc.
PowerPoint Lecture prepared by
Jill Feinstein
Richland Community College
1 The Process of Science
 Science refers to a body of knowledge
 Science is not a giant collection of facts to be
memorized.
 It important to learn about the process of science
called the scientific method.
 The scientific method allows the solving of
problems and answer questions.
 Observations
 Proposing ideas
 Testing the ideas
 Discarding or modifying ideas based on results
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1 The Process of Science
The Nature of Hypotheses
 Hypothesis: proposed explanation for a set of
observations
 Hypotheses needs to be:
 Testable – it must be possible to examine the
hypothesis through observations
 Falsifiable – it must be able to potentially be
proven false
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1 The Process of Science
Where do hypotheses come from?
 Both logical and creative influences are used to
develop a hypothesis
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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
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1 The Process of Science
The Logic of Hypothesis Tests
 Inductive reasoning: combining a series of
specific observations into a generalization to
create a hypothesis
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1 The Process of Science
The Logic of Hypothesis Tests
 To test the hypothesis use deductive reasoning:
 This involves using a general principle to predict
an expected observation using if/then statements
 For example, If vitamin C decreases the risk of
catching a cold, then people who take in additional
Vitamin C will get less colds.
© 2013 Pearson Education, Inc.
1 The Process of Science
The Logic of
Hypothesis Tests
 The process looks
something like this:
© 2013 Pearson Education, Inc.
1 The Process of Science
© 2013 Pearson Education, Inc.
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.
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2 Hypothesis Testing
 The most powerful way to test hypotheses: do
experiments
 Experiments support the hypothesis that the
common cold is caused by a virus.
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2 Hypothesis Testing
The Experimental Method
 Experiments are designed to collect data or
information 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
© 2013 Pearson Education, Inc.
2 Hypothesis Testing
Controlled Experiments
 Controlled experiment: tests the effect of a
single variable
 Control: a subject who is not exposed to the
experimental treatment but has all other variables
the same
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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
© 2013 Pearson Education, Inc.
Animation: Science as a Process: Arriving at Scientific Insights
Click “Go to Animation” / Click “Play”
© 2013 Pearson Education, Inc.
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.
© 2013 Pearson Education, Inc.
2 Hypothesis Testing
Controlled Experiments
 People who received
echinacea tea felt that
it was 33% more effective
at reducing symptoms.
© 2013 Pearson Education, Inc.
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 don’t 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 gropu until after the
experiment is over
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2 Hypothesis Testing
Minimizing Bias in Experimental Design
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2 Hypothesis Testing
Using Correlation to Test Hypotheses
 The “gold standard” for experimentation
 Double-blind, placebo controlled and randomized
experiments
 Model systems can be used in experiments
when it appears to 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 is
impossible to perform
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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?
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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.
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2 Hypothesis Testing
Using Correlation to Test Hypotheses
 The correlation might be due to other reasons.
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2 Hypothesis Testing
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3 Understanding Statistics
Overview: What Statistical Tests Can Tell Us
 Statistics in science is used to evaluate and
compare data.
 We can extend the results from small samples to an
entire population using statistical tests.
 Statistically significant: results of difference
between groups is due to random chance and not
an error in experimenting
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3 Understanding Statistics
The Problem of Sampling Error
 Sampling error: the effect of chance on
experimental data
 We can calculate the probability that a result is
simply due to sampling error.
 Confidence interval: the range of values from a
sample that has a 95% probability of containing the
true population mean (average)
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3 Understanding Statistics
The Problem of Sampling Error
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3 Understanding Statistics
Factors that Influence Statistical Significance
 Sample size
 The true difference between populations
 Bigger is better: more likely to detect differences
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3 Understanding Statistics
Factors that Influence Statistical Significance
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3 Understanding Statistics
What Statistical Tests Cannot Tell Us
 If an experiment was designed and carried out
properly
 If observer error occurred, only can evaluate the
probability of sampling error
 May not be of any biological significance
© 2013 Pearson Education, Inc.
4 Evaluating Scientific Information
Primary Sources
 Researchers can submit a paper about their 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
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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
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4 Evaluating Scientific Information
Science in the News
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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.
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4 Evaluating Scientific Information
Understanding Science from Secondary Sources
 Use your understanding of the process of science to
evaluate science stories.
 News media generally highlight only those science
stories that seem newsworthy.
 They are more likely to report a positive result than
a negative one.
© 2013 Pearson Education, Inc.
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
© 2013 Pearson Education, Inc.
A(n) ________ is a proposed explanation for a
single observation.

scientific method

hypothesis

scientific theory

experiment
© 2013 Pearson Education, Inc.
A(n) ________ is a proposed explanation for a
single observation.

scientific method

hypothesis

scientific theory

experiment
© 2013 Pearson Education, Inc.
Which of the following is a scientific hypothesis?

Jazz is better music than rap.

Garden fairies make tomatoes grow better.

Hunting species to extinction is wrong.

Increasing the amount of protein in a cow’s
diet increases her milk yield.
© 2013 Pearson Education, Inc.
Which of the following is a scientific hypothesis?

Jazz is better music than rap.

Garden fairies make tomatoes grow better.

Hunting species to extinction is wrong.

Increasing the amount of protein in a cow’s
diet increases her milk yield.
© 2013 Pearson Education, Inc.
Which of the following is correct?

A hypothesis can be wrong.

A hypothesis is not always testable.

A hypothesis can prove a person’s values.

A hypothesis should be formed before making
any observations.
© 2013 Pearson Education, Inc.
Which of the following is correct?

A hypothesis can be wrong.

A hypothesis is not always testable.

A hypothesis can prove a person’s values.

A hypothesis should be formed before making
any observations.
© 2013 Pearson Education, Inc.
Which of the following statements was developed
using deductive reasoning?

People who take in large amounts of caffeine
are irritable.

If subjects take in large amounts of caffeine,
then it will increase irritability.

Large amounts of caffeine has shown to
increase irritability.

Irritability has been shown to increase with a
decrease in caffeine consumption.
© 2013 Pearson Education, Inc.
Which of the following statements was developed
using deductive reasoning?

People who take in large amounts of caffeine
are irritable.

If subjects take in large amounts of caffeine,
then it will increase irritability.

Large amounts of caffeine has shown to
increase irritability.

Irritability has been shown to increase with a
decrease in caffeine consumption.
© 2013 Pearson Education, Inc.
In an experiment, Dr. Smith feeds different
amounts of protein to dairy cows and measures the
differences in their milk yields. What is the
independent variable in Dr. Smith’s experiment?

time

milk yield

amount of protein

placebo
© 2013 Pearson Education, Inc.
In an experiment, Dr. Smith feeds different
amounts of protein to dairy cows and measures the
differences in their milk yields. What is the
independent variable in Dr. Smith’s experiment?

time

milk yield

amount of protein

placebo
© 2013 Pearson Education, Inc.
What is happening in step #2 in the diagram?

The virus is introducing its
genetic material into the
cell.

The host cell is killed.

Copies of the virus
are being made by
the host cell.

The virus is being
destroyed by the host cell.
© 2013 Pearson Education, Inc.
What is happening in step #2 in the diagram?

The virus is introducing its
genetic material into the
cell.

The host cell is killed.

Copies of the virus
are being made by
the host cell.

The virus is being
destroyed by the host cell.
© 2013 Pearson Education, Inc.
What does this graph show?

There is no difference between
placebo and zinc lozenges.

Taking placebo lozenges
causes people to have more
types of cold symptoms.

Zinc lozenges lead to people
catching fewer colds.

People taking zinc lozenges
show cold symptoms for a
shorter period of time.
© 2013 Pearson Education, Inc.
What does this graph show?

There is no difference between
placebo and zinc lozenges.

Taking placebo lozenges
causes people to have more
types of cold symptoms.

Zinc lozenges lead to people
catching fewer colds.

People taking zinc lozenges
show cold symptoms for a
shorter period of time.
© 2013 Pearson Education, Inc.
The confidence interval is the range of values that
has a _____ probability of containing the true
population mean.

5%

30%

75%

95%
© 2013 Pearson Education, Inc.
The confidence interval is the range of values that
has a _____ probability of containing the true
population mean.

5%

30%

75%

95%
© 2013 Pearson Education, Inc.
A statistical test evaluates the chance of _______.

observer error.

sampling error.

alternative mechanisms.

need for controls.
© 2013 Pearson Education, Inc.
A statistical test evaluates the chance of _______.

observer error.

sampling error.

alternative mechanisms.

need for controls.
© 2013 Pearson Education, Inc.
Which of these statements about primary and
secondary sources are correct?

Primary sources are written by researchers;
secondary sources are written by book authors,
news reporters, and advertisers.

Primary sources aren’t biased; secondary sources
are biased.

Primary sources are not peer reviewed; secondary
sources are peer reviewed.

Primary sources are less reliable; secondary
sources are more reliable.
© 2013 Pearson Education, Inc.
Which of these statements about primary and
secondary sources are correct?

Primary sources are written by researchers;
secondary sources are written by book
authors, news reporters, and advertisers.

Primary sources aren’t biased; secondary sources
are biased.

Primary sources are not peer reviewed; secondary
sources are peer reviewed.

Primary sources are less reliable; secondary
sources are more reliable.
© 2013 Pearson Education, Inc.
What is the best way to prevent the common cold?

Take vitamin C.

Wash your hands.

Take zinc lozenges.

Get a cold vaccine.
© 2013 Pearson Education, Inc.
What is the best way to prevent the common cold?

Take vitamin C.

Wash your hands.

Take zinc lozenges.

Get a cold vaccine.
© 2013 Pearson Education, Inc.