Unit 3: Credibility of Health
Claims
Credibility of health claims
• How do you know what to believe?
• What makes information reliable?
• Can you really lose 10 lbs of belly fat in 2
weeks?
Evidence
• When you read or hear something, ask yourself what kind
of evidence is provided. Don’t just believe everything you
hear!
• Scientists, like lawyers, rely on evidence to support a point
• There are different types of evidence, some more reliable
than others:
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1. Experimental
2. Epidemiological
3. Clinical
4. Personal
5. Anecdotal
1. Experimental Evidence
• Proper scientific evidence is often produced
by well designed experimental evidence
(think “experiments”)
• All experiments must begin with a hypothesis
– “hypothesis” = something you are trying to prove
phrased in a way that can be tested
Testing your Hypothesis
• To test your hypothesis you will need a group of people
(sample) who are representative of the population you are
trying to study.
• Your sample should be randomly selected and then
randomly allocated into one of two groups:
• Experimental group = the group of subjects receiving the
experimental treatment
• Control group = the group that is used as a way to control
the effect of other factors.
– Often receive a placebo
– Placebo = something that has no effect on the variable being
tested and that the subjects cannot tell is different from the real
experiment
Testing Your Hypothesis
• You should take baseline measurements at
the beginning of your trial and then observe
and record results as the study progresses to
completion
• Statistics are often then used to compare
baseline measurements with final results and
to compare the experimental group with the
control group
Hallmarks of a quality experiment
• blind study: when the subjects do not know
whether they are receiving the treatment
(experimental group) or not (control group)
• double-blind (preferred): when neither the
subjects nor the researchers know which group
is receiving the treatment and which is not
Hallmarks of a quality experiment
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Large sample size
Random selection
Representative sample
Informed consent
Common experimental problems
• Time
• Ethical consideration
– Other Options
• Animal experimentation
• Tissue cultures
• Computer Modeling
2. Epidemiology
• Epidemiology “is the study of how often diseases occur
in different groups of people and why. Epidemiological
information is used to plan and evaluate strategies to
prevent illness and as a guide to the management of
patients in whom disease has already developed.” -BMJ
• There is no manipulation of variables
• We observe trends, report on them, try to find
associations and figure out why trends have been
reported
Epidemiology of HIV infection
An epidemiologist would ask: what are the reasons for these trends?
Epidemiology and Causation
• Wait! Even if an association is found between two
variables, remember:
• Association does not equal causation!
• For an association to be considered causal, the
following characteristics of the association are taken
into account
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6.
Strong association?
Dose Response relationship?
Consistency of results?
Temporal correctness?
Specificity?
Biological plausibility?
3. Clinical Evidence
 Comes from the experience of clinicians
doctors, dentists, nurses, psychologists, athletic
trainers etc.
 Reflects what a clinician notices in his or her
practice
4. Personal Experience
 What you have experienced in your own life
 Ex. “ when I eat too much bread I gain weight”
 NOT a valid source of health information
5. Anecdotal Evidence
• Anecdote= a story someone tells you
• Although powerful, NOT a reliable source of health
information
Critical Thinking
 Must separate scientific evidence from opinion
 Use the following criteria to help determine whether
the information you are reading is a quality
representation of scientific evidence:
1. Reliable source?
2. Recent date?
3. Author’s qualifications?
4. Sufficient evidence?
5. Bias?
6. Faulty reasoning?
Evaluating Health Information