It turns out that you only need 23 people for it to be more likely to find a shared birthday than not. - David Franklin

The Google team at Project Aristotle concluded that there were five main traits of a successful team. Psychological safety was the most important, and their research suggested that it underpinned the other four[xxvi]. The five traits were as follows: (1) Psychological safety: team members feel safe to take risks and be vulnerable in front of each other. (2) Dependability: team members get things done on time, and meet Google’s high bar for excellence. (3) Structure and clarity: team members have clear roles, plans, and goals. (4) Meaning: work is personally important to team members. (5) Impact: team members think their work matters and creates change.

Dan asks the class whether any of them has ever checked the weather on their phone to see if it’s likely to rain while they’re outside. Everyone has. “What do you do if you see there’s a 30% chance of rain?” “Take an umbrella”, several students all say at once.

The great economist John Maynard Keynes is supposed to have said “when the facts change, I change my mind. What do you do, sir?