Who Do You Trust?

Dr. Kim is a renowned climate scientist who has accurately predicted 90% of the major climate events over the past decade. She now predicts a severe storm will hit the coast next week. How confident should you be in her prediction?

• 100% confident

• 90% confident

• 10% confident

• 50% confident

Alice has been successfully managing her investments for over 30 years, so her investment decisions are carefully watched by other investors. 85% of the time that she buys 100 or more shares in a company that company’s stock price rises within a week. 75% of the time that she buys 50 or more shares in a company that company’s stock price rises within a week. But, strangely, only 55% of the time that she buys precisely 20 shares in a company does that company’s stock price rise within a week. Today, Alice buys 15 shares of ACME. How confident should you be that ACME’s stock price will rise within a week?

• Less than 50% confident

• 10% confident

• Between 75% and 85% confident

• The information given above does not help to answer this question

Which of the following factors is most important in deciding whether or not to trust someone’s testimony?

• How confident she sounds when delivering that testimony

• How confident she looks when delivering that testimony

• The quality of her character in general

• How accurate her testimony has been recently on topics like the one that she’s talking about now

Njeri is an expert astronomer, and she has been watching with concern as an asteroid moves closer and closer to the Earth. On the basis of her observations, Njeri claims that there is a 100% chance that the asteroid will hit the Earth. She has announced a 100% chance of asteroid contact only 20 times in her career, and she has been right 17 of those times. How confident should you be that the asteroid will hit the Earth?

• 50% confident

• 5% confident

• 85% confident

• 100% confident

Maria is a seasoned chef known for her ability to perfectly cook steaks 95% of the time. She is preparing a steak dinner for a special event tonight. How confident should you be that the steak will be perfectly cooked?

• 50% confident

• 5% confident

• 100% confident

• 95% confident

The ACY is a standardized test given to all high school seniors in Fredonia. 85% of the students who score a 30 or higher on the ACY will graduate from university. Akiko is one of 10 students who have just scored a 25 on the ACY. How confident should you be that Akiko will graduate from university?

• 50% confident

• 10% confident

• 100% confident

• The information given above does not help to answer this question

Nate has been forecasting the results of horse races,and makes a correct prediction 85% of the time. Today, Nate predicts that Silverado will win the horse race. Today’s horse race (like most of the others that Nate has considered) is a race among 10 horses. There is nothing that specially distinguishes today’s horse race from others or that distinguishes Silverado from other horses that Nate has predicted to win. How confident should you be that Silverado will win?

• 50% confident

• 10% confident

• 85% confident

• 100% confident

Jordan is a professional chess player who wins 80% of his matches against players ranked in the top 100. Today, he is playing against a player ranked 95th. How confident should you be that Jordan will win the match?

• 80% confident

• 20% confident

• 50% confident

• 100% confident