Probability

Question 1

What is base rate neglect?

Answer 1

Ignoring pre test probability

Question 2

What is anchoring bias?

Answer 2

is a cognitive bias that causes us to rely heavily on the first piece of information we are given about a topic

Question 3

What is confirmation basis?

Answer 3

cognitive bias that favors information that confirms your previously existing beliefs or biases

Question 4

How is probability expressed?

Answer 4

1-100% (0-1)

Question 5

What can overestimated probability lead to?

Answer 5

1. Medication overuse & excessive procedure
2. Corrupt shared decision making with patients.

Question 6

What are biases?

Answer 6

substitute judgements of representativeness for judgements of actual probability

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

Question 7

T or F
“An uncommon presentation of a common disease is more likely than a common presentation of a rare disease”

Answer 7

True

Question 8

Bayesian reasoning essential keys (2)?

Answer 8

1. Anchor your judgement of the probability to a plausible base rate (pretest probability)
2. Question the diagnosticity of your evidence

Diagnosticity: the extent to which a source of data can discriminate between a particular hypothesis and its alternatives

Question 9

What is pre-test & post test probability?

Answer 9

Pre test: The estimate of a disease probability before you do a test

Post test: The probability after doing a test

Question 10

What is the best reference class?

Answer 10

the set of patients that most closely matches the current patient

Question 11

What is a basic reference class? Pros & cons of it?

Answer 11

The prevalence of a disease in a population.
-prevalence: The proportion of the population affected by a condition

Pros:
1. relatively easy to search for
2. can specify for sub populations for more accurate estimate (Canadian women)

Cons:
1. May be an underestimate if it is something that people frequently seek medical attention for
2. Less helpful for acute conditions

Question 12

What is a more specific reference class? Pros & cons?

Answer 12

Studies that give eventual diagnosis in patients presenting with complaints similar to your patients.

Pros:
1. Takes the presenting symptom into account to provide a more accurate initial judgement.
2. Takes into account people tend to seek medical conditions more than others.

Cons:
1. This research is less common (harder to find)
2. Clinical scenario in research may be different than your own.

Question 13

What to NOT use for reference class & why?

Answer 13

1. incidence in the population
   - the frequency of a disease over time
2. lifetime prevalence
   -the chances of developing a disease over a lifetime

These will tend to be an overestimate