unit 3: credibility of health claims. credibility of health claims how do you know what to believe?...

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:– 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

• 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

1. Strong association?2. Dose Response relationship?3. Consistency of results?4. Temporal correctness?5. Specificity?6. Biological plausibility?

3. Clinical Evidence

Comes from the experience of cliniciansdoctors, 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 lifeEx. “ 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 ThinkingMust 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