week 4 Flashcards
probability
-how likely something is
-usually expressed on a scale of 0-100% (or 0-1)
-it is not possible by rationally updating ones view, to reach complete certainty (0 or 100%), although you can approach this
-it follows that you will need to act before you are certain
-consider probability for better decision making in the context of uncertainty
overestimation
-overestimated probability of diagnosis before and after testing
-this overestimation is consistent with cognitive biases, including base rate neglect, anchoring bias, and confirmation bias
-can result in medication overuse and excessive procedures with their associated harms
-could corrupt shared decision-making with patients because practitioners need to understand the likelihood of various outcomes in order to communicate them (training in shared decision-making has often focused on communication skills, not on actually understanding the probability of disease)
shared decision making
between practitioner and patient
representativeness
the degree to which something is representative of, or similar to, the stereotype
biases- representativeness
-substitute judgements of representativeness for judgments of actual probability
-representativeness: the degree to which something is representative of, or similar to, the stereotype
i.e. librarian or farmer
don’t do based on characteristics do as a statistician based on probability -how many of each of these professions
an uncommon presentation of a common disease is more likely that a common presentation of a rare disease
bias
bayesian reasoning (biases):
-anchor your judgement of the probability of an outcome on a plausible base rate (i.e. pretest probability)
-question the diagnosticity of your evidence
pre-test probability
-best estimate of a disease probability before you do a test
-a starting place rom which to update probability
-multiple ways to determine this but want to start with a good reference class
-best reference class: the set of patents that most closely matches this patient
post-test probability
-best estimate of a disease probability after doing a test
best reference class for pretest probability
-best reference class: the set of patents that most closely matches this patient
reference classes (basic)
-basic: the prevalence of a disease in a population
–> prevalence: the proportion of a population affected by a condition
pros:
-relatively easy to search for
-can specify sub-populations to get a more accurate estimate
cons:
-may be an underestimate if it is something that people frequently seek medical attention for
-less helpful for acute conditions
prevalence
prevalence: the proportion of a population affected by a condition
reference classes (more specific)
-more specific: studies that give eventual diagnosis in patients presenting with complaint(s) similar to your patients
pros:
-take the presenting symptom into account to provide a more accurate initial judgement
-takes into account that people tend to seek medical attention fro some conditions more than others
cons:
-this research is less common (harder to find)
-clinical scenario in research may be different from your own
DO NOT USE: reference classes
-incidence in the population
–> the frequency of a disease over a period of time
-lifetime prevalence
–> the chances of developing the disease over a lifetime: will tend to be an overestimate
