What is the difference between critical thinking and critical appraisal? Essentially both are intellectual disciplines that seek to examine the basis of claims made and their veracity. In my view, they are complimentary skills.
What unites critical appraisal and critical thinking is a concern for the adequacy of the justification of conclusions. The oft-cited phrase in medicine: "What is your evidence" is a request for a justification of the choice of diagnostic test or therapeutic intervention. The point of this course is to demonstrate that not all justifications are equal and that some are sounder than others. This is what we mean by reasoning skills.
al. have defined critical appraisal as "the application of rules
of evidence to clinical (signs and symptoms), paraclinical (laboratory
and other diagnostic tests) and published data (advocating specific treatment
maneuvers or purporting to establish the etiology or prognosis of disease
in order to determine their validity (closeness to the truth) and applicability
(usefulness in one's clinical practice). Critical appraisal then is focused
primarily on "evidence" derived from empirical research studies
published in the scientific literature.
Unfortunately, as the authors of this influential textbook point out, you cannot critically appraise editorials or arguments for that matter. Critical appraisal is indispensable as a technique for evaluating the strength of factual claims in health care. However, it is addressed only to the facts and not to the arguments.
Critical thinking looks at arguments that use both facts and value claims and seeks to assess the soundness of such arguments. It can be defined as follows:
Argument analysis and critical appraisal should be viewed as complimentary skills. Critical appraisal consists of a set of questions to be posed of empirical studies in health care. These questions are designed to assist readers in determining how well the study has been designed and carried out in order to determine whether the results are credible. The critical appraisal frameworks should not be seen as guarantors of the truth of a study. They are best regarded as heuristic tools.
you are familiar with critical appraisal, you can move on to the next
section of the course. If you are not familiar with critical appraisal,
we recommend you visit the following sites and familiarize yourself with
critical appraisal and evidence based medicine.
component of argument analysis is the detection of fallacies. Fallacies
are defined as arguments that appear to be valid, but are in fact invalid.
We must remember that in logic, validity refers to the inferences from
premises to conclusions. This is very different from the way the term
is used in health care and epidemiology where validity often is used synonymously
with truth. An invalid argument is one that cannot be credible, that is,
there is no reason to accept the truth of the conclusion as it does not
follow from the premises.
The closest analogue to a fallacy in the
critical appraisal of studies is bias. Bias occurs when faults in study
design lead to a misrepresentation or distortion of the relationship between
an exposure (such as a drug) and an outcome (such as cancer or reduction
of blood pressure). A biased estimate is incorrect, and like an invalid
argument, lacks credibility.
There are many fallacies that have been identified in informal logic. We provide here a set of links to sites that have catalogues of fallacies:
particular interest is the following site that catalogues fallacies according
to where they can occur in the framework
of the Toulmin diagram.
are interested in starting a collection of examples of fallacious reasoning
around health care topics. If you find examples in the media or in the
published medical literature, we encourage you to submit them to us. We
will be posting them here on the Exercises section of our website.