Unit 3: Credibility of Health Claims

Unit 3: Credibility of Health
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
• When you read or hear something, ask yourself what kind
of evidence is provided. Don’t just believe everything you
• Scientists, like lawyers, rely on evidence to support a point
• There are different types of evidence, some more reliable
than others:
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
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
• 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
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
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
Strong association?
Dose Response relationship?
Consistency of results?
Temporal correctness?
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
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
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