Cognitive Reflection Test Cognitive Reflection Probability and Statistical Intuition

Question 1

A disease affects 1 in 1,000 people. A test for it is 99% accurate. You test positive. What is the approximate probability you actually have the disease?

Accepted Answer

About 9%

Answer

About 99%

Answer

About 50%

Answer

About 1%

Question 2

A fair coin is flipped 5 times and lands heads each time. What is the probability the next flip is heads?

Accepted Answer

Exactly 50%

Answer

Less than 50% — it's 'due' for tails

Answer

More than 50% — heads is on a streak

Answer

Cannot be determined

Question 3

In a group of 23 people, what is the approximate probability that two share a birthday?

Accepted Answer

About 50%

Answer

About 5%

Answer

About 25%

Answer

About 75%

Question 4

If you flip a fair coin twice, what is the probability of getting at least one head?

Accepted Answer

75%

Answer

25%

Answer

50%

Answer

100%

Question 5

A bag has 3 red and 7 blue marbles. You draw one without looking. What is the probability it is red?

Accepted Answer

30%

Answer

3%

Answer

10%

Answer

70%

Question 6

Two independent events each have a 50% probability of occurring. What is the probability BOTH occur?

Accepted Answer

25%

Answer

100%

Answer

50%

Answer

10%