Probability

Question 1

True or False: It is not possible by rationally updating one’s views, to reach complete certainty (0 or 100%), although you can approach this

Answer 1

TRUE

Question 1

probability is

Answer 1

how likely something is

Question 2

the degree to which something is representative of, or similar to, the stereotype

Answer 2

representativeness

Question 3

2 heuristics for avoiding bias:

Answer 3

1. Anchor your judgement of the probability of an outcome on a plausible base rate (ex. pretest probability)
2. question the diagnosticity of your evidence

Question 4

pre-test probability

Answer 4

best estimate of a disease probability before you do a test

Question 5

the set of patients that most closely matches this patient

Answer 5

reference class

Question 6

prevalence

Answer 6

the proportion of a population affected by a condition

Question 7

example of a basic reference class

Answer 7

the prevalence

Question 8

Pros to using prevalence as a reference class

Answer 8

• easy to search for
• you can specify sub-populations to get a more accurate estimate

Question 9

Cons to using prevalence as a reference class

Answer 9

• might be an underestimate if it is something that people frequently seek medical attention for
• less helpful for acute conditions (prevalence doesn’t last long)

Question 10

ex. of a more specific reference class studies that give an eventual diagnosis in patients presenting with a complaint(s) similar to your patient’s

Question 11

Pros to using a more specific reference class

Answer 11

• take the presenting symptom into account to provide a more accurate initial judgement
• takes into account that people tend to seek medical attention for some conditions more than others

Question 12

Cons to using a more specific reference class

Answer 12

• This research is less common (harder to find)
• clinical scenarios in research may be different from your own

Question 13

what reference class should you not use:

Answer 13

• incidence in the population
• lifetime prevalence

Question 14

what is incidence

Answer 14

it is the frequency of a disease over a period of time

Question 15

what is lifetime prevalence?

Answer 15

the chances of developing the disease over a lifetime: will tend to be overestimated

Question 16

What is a good tip to consider when finding pre-test probability?

Answer 16

• consider finding different reference classes with the useful methods above to represent maximum and minimum estimates
• consider adding pretest probabilities to illness scripts