Judgements and probabilities - RD3

Question 1

What is a judgement?

Answer 1

calculating the likelihood of events using incomplete information (e.g 68% likely to happen)

Question 2

How are judgements different from decisions?

Answer 2

judgements are the probabilities of each option being correct, decisions are the actual option you choose (usually the one with the highest probability)

Question 3

what are hits and correct rejections also known as?

Answer 3

hits = sensitivity
correct rejection = specificity

Question 4

What do people aim to do when creating tests for diseases?

Answer 4

maximise hits and correct rejections

Question 5

Even if a test is the same accuracy, what can affect the chance that someone with a positive result actually has a disease?

Answer 5

base rate

Question 6

What is Bayes rule? what do the components mean?

Answer 6

Posterior ∝ likelihood x prior
- posterior = updated belief that you have a disease (given the data)
- likelihood = probability of the test result give prior
- prior = base rate (probability of having the disease)

Question 7

what is the fraction used to calculate posterior odds?

Answer 7

the probability of not having the disease given the evidence/the probability of having the disease given the evidence

Question 8

what is the fraction used to calculate likelihood ratio?

Answer 8

the probability of getting a positive result given that you don’t have the disease/the probability of getting a positive result given that you have the disease

Question 9

what is the fraction used to calculate the prior odds?

Answer 9

the probability of not having the disease/the probability of having the disease

Question 10

What numbers from the efficacy of a test do you use when working out the likelihood ratio?

Answer 10

the false alarm rate and the hit rate

Question 11

what numbers do you use when working out the prior odds?

Answer 11

The prevalence of the disease and 100- the prevalence

Question 12

How does the engineer/lawyer study by Kahneman and Tversky (1973) show base rate neglect?

Answer 12

Participants thought the person was more likely to be an engineer after hearing about his character, while ignoring that most people in his group are lawyers so logically he’s more likely to be a lawyer

Question 13

What did cascells et al (1978) find when they told medical students the prevalence of a disease and the false positive rate?

Answer 13

• base rate neglect
• just used the false positive rate to work out how likely they would be to have the disease with a positive result

Question 14

What is the conjunction fallacy?

Answer 14

the mistaken assumption that the probability of the conjunction of 2 events is greater than the probability of one of them

Question 15

Why might we fall for the conjunction fallacy?

Answer 15

we value precision/specificity and assume that information in both options is redundant

Question 16

What did Tversky and Kahneman (1983) find in the bank teller problem?

Answer 16

people said that linda was more likely to be a bank teller who is in the feminist movement than just a back teller
conjunction fallacy

Question 17

Even though many say we aren’t optimal, what things can improve our performance? (3)

Answer 17

• including info about causal structure
• presenting in frequentist terms
• personal relevance to the problem

Question 18

What is the representativeness heuristic?

Answer 18

assume an object/individual belongs to a specific category because it is representative

Question 19

What is the availability heuristic?

Answer 19

frequencies of events are estimated by ease of retrieval

Question 20

What did Lichenstein (1978) find when looking at how commonly people rated causes of death?

Answer 20

Publicised deaths were rated as more common - e.g murder and suicide

Question 21

What are the biggest drivers for how commonly people will rate a disease according to Pachur et al (2012)? (3)

Answer 21

• direct experiences (biggest driver)
• emotional response (affect heuristic)
• media coverage

Question 22

What are 4 problems with heuristics as a theory for how we judge?

Answer 22

• they are vaguely defined
• doesn’t define when specific heuristics are used
• not necessarily biased processing but poor information
• a list doesn’t equate to a ‘theory’

Question 23

What is the dual-process theory?

Answer 23

judgements are based on 2 distinct systems: system 1 (fast, automatic, effortless, implicit) and system 2 (slow, serial, effortful, controlled)

Question 24

In dual-process theory, when do we use the different systems? What is the problem with us and our use of the systems?

Answer 24

use system 1 most (heuristics) - but this is not optimal and is prone to errors
cognitive misers - we can use system 2 to get the right answer but will often use 1 because it’s easier

Question 25

What are some problems with the dual-process theory? (4)

Answer 25

• system 2 also leads to errors sometimes
• could be more of a continuum, not a hard distinction
• both systems are relatively ill-defined
• some evidence for intuitive use of base rate (system 1)

Question 26

Which rules do we use when deciding which city is bigger? (3)

Answer 26

• search rule - do I know the city or anything about it?
• stopping rule - stop search if you only know one city
• decision rule - choose the city you know

Question 27

How did telling people a city had an airport change their estimates of its size compared to a known city? What does this tell us?

Answer 27

Mostly still based on recognition but not as much as if they weren’t told about the airport
so they used relevant information to help them

Question 28

What is the correlation between the validity of the information of knowing a city and its usage?

Answer 28

.64
don’t go on recognition as much if that’s not helpful, like judging the northness of a city