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Chapter 1
 Introduction to the Scientific Method
Can Science Cure the Common Cold?

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 Science is the process of discovering
something new
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QUESTION

Scientific theory

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1 The Process of Science
Scientific Theory
 Powerful, broad explanation of a large set of
observations
 Rests on many hypotheses that have been
tested
 Generates additional hypotheses
 Some scientific theories include the theory of
evolution, the theory of relativity, the atomic
theory, and the quantum theory
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 Involves using general principle to predict an
expected observation
 “if…then” statement

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1 The Process of Science
The Logic of
Hypothesis Tests
 The process looks
something like this:

Hypothesis
(that is testable and fasifiable)
Consuming vitamin C reduces
the risk of catching a cold
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Test prediction
Conduct experiment or survey
to compare number of colds
in people who do and do not
take vitamin C supplements
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1 The Process of Science

If people who
take vitamin C
suffer fewer
colds than
those who do
not
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Conclude that
prediction is
true

Conclude that
prediction is
false

Do not reject
the hypothesis

Reject the
hypothesis

Conduct
additional
tests

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3 (continued)

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 A hypothesis that passes is supported, but
not proven
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Important: A hypothesis is never
proven true! Just supported
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 Example:
 In 1970 Nobel-prize winning chemist Linus
Pauling claimed that vitamin C reduced
susceptibility to colds
 His claim was based on a few studies
 Today most health scientists agree that
vitamin C does not prevent colds

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2 Hypothesis Testing
 The most powerful way to test hypotheses:
do experiments

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2 Hypothesis Testing
 Experiments support the hypothesis that the
common cold is caused by a virus
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Virus

Protein
shell

Throat

Genetic
material and
proteins
Virus
copies

2 The viral genetic material instructs the
host cell to make new copies of the
virus
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Side effects are
increased mucus production and throat
irritation
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These
copies can infect other cells in
the same person or cells in
another person (for example, if
transmitted by a sneeze)
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2 Hypothesis Testing
The Experimental Method
 Experiments are contrived (artificial)
situations in which scientist collect data about
a variable they are testing
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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
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 Both groups rated the effectiveness of
their treatment on relieving cold
symptoms
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 Blind experiment: subjects don’t know what
kind of treatment they have received
 Double blinding: the person administering
the treatments also doesn’t know until after
the experiment is over
 Double blind, placebo-controlled, randomized
experiment is the “gold standard”
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2 Hypothesis Testing
 To summarize……
 Eliminating bias (a predetermined idea) is
done by using blind or double blind
experiment
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 In experiments that are potential dangerous
to humans we can use model organisms
(mice)

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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
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2 Hypothesis Testing
Using Correlation to Test Hypotheses
 Caution! Correlation does not imply
causation
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 Example: There is a correlation between cold
weather and incidence of cold illness
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When
temperatures are cold people stay indoors
and contact is increased
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2 Hypothesis Testing
Using Correlation to Test Hypotheses
A correlation typically cannot eliminate all
alternative hypothesis

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 This is done by random sampling
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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
What Statistical Tests Cannot Tell Us
 If an experiment was designed and carried
out properly
 Was bias eliminated or reduced?
 Was the sample selected in a random manner
so that it was a good representation of the
population?

 Evaluate the probability of sampling error, not
observer error
 May not be of any biological significance
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4 Evaluating Scientific Information
Primary Sources
 Researchers can submit a paper about their
results to a professional journal (primary
source)
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 Example: a testimonial from a celebrity

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4 Evaluating Scientific Information
Science in the News
 Secondary sources may be missing critical
information or report the information
incorrectly
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4 Evaluating Scientific Information
Science in the News
 Be careful with the internet since anyone can
post information
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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
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 They are more likely to report a positive result
than a negative one
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 Wash your hands!
 No effect on cold
susceptibility:
 Vitamin C
 Exposure to cold temperatures
 Exercise

 No vaccine for the common
cold
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 Can a scientific hypothesis be proven true?
 Answer: No, because even if the experiment
supports the results there may be another
possible explanation

 Scientific methods cannot determine absolute
truth
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Practice question
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 True
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Then statements

 How can you ensure that the experiment will
better represent the population as a whole?
( see slides 20, 21, 27)
 How can you eliminate bias from an
experiment?
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 What is the independent variable in the
Echinacea tea experiment?
 What hyposthesis was tested by Warren and
Marshall during their research involving the
Helicobacter bacteria?
 If an experiment is too dangerous or
unethical for humans, what can you do?

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