A checklist for big decisions
Knowing about thinking errors doesn't stop them; a routine does. A short checklist, with the outside view and a pre-mortem, catches most of the errors in this path before they cost you.
PsychologyThink clearlyAbout 6 min: 4 reading, 2 practiceUpdated
Educational, not medical or mental-health advice.
- Explain the planning fallacy and use the outside view to correct it
- Run a pre-mortem on a plan
- Use a six-question checklist before a big decision
Builds toward: Think clearly. Catch common thinking errors in yourself and in other people's arguments, and make better calls when you can't be sure.
Think clearly: thinking errors and better decisions: lesson 7 of 7
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Pairs with Kahneman, Lovallo and Sibony (2011), "Before you make that big decision"; Klein (2007), "Performing a project premortem"; Buehler, Griffin and Ross (1994)
What it is
The thinking errors in this path are hard to see from the inside. Reading about them helps a little; a routine helps a lot. Pilots and surgeons use checklists for the same reason: not because they don't know what to do, but because a checklist catches what a busy mind skips.
This lesson adds two tools to the checklist, then puts it together.
The outside view. We usually plan from the inside view: our own plan, step by step, imagining it going well. The outside view asks instead: how did similar cases go for other people? Starting from that reference class corrects the planning fallacy, our habit of underestimating how long and how much things take.
Quick check
Tap an answer to check it.
You think your kitchen renovation will take 4 weeks. Which question takes the outside view?
- That is the inside view: your own plan, imagined going well
Show answer
How long did similar renovations take for people I know, or in published figures?. The outside view starts from how similar projects actually went, then adjusts for what is special about yours.
Why it matters
The planning fallacy. In a study by Buehler, Griffin and Ross (1994), final-year students predicted when they would finish their thesis. On average they predicted about 34 days; it took about 56. Only about 30% finished by the date they had predicted. They knew past projects had overrun, but didn't apply that to this one.
The checklist below gathers the defences from this path into one routine you can use in ten minutes:
| # | Question | Catches |
|---|---|---|
| 1 | What are at least three options, including doing nothing? | Narrow framing |
| 2 | How did similar decisions go for others? (outside view) | Planning fallacy, availability |
| 3 | Where did my numbers come from? Did I set them before hearing anyone else's? | Anchoring |
| 4 | What would change my mind, and have I looked for it? | Confirmation bias |
| 5 | How does it look framed as a gain, and as a loss? | Framing, loss aversion |
| 6 | It's a year later and it failed: why? (pre-mortem) | Overconfidence |
Then write down your decision and your reasons, so you can check later how your judgement did, rather than remembering it more kindly than it was.
Worked example
Jo is deciding whether to take a job in another city: higher pay, longer hours.
- Options: take it; stay; ask the current employer for a raise; keep looking for six months.
- Outside view: two friends made similar moves; both found the first year lonelier and costlier than expected. Jo adds a cost-of-living check: rent there is 3,600 a year higher.
- Numbers: the "20% raise" was the recruiter's headline, before tax. Jo works it out in take-home pay instead: about 2,600 a month now, about 3,050 there, so about 5,400 a year more. After the higher rent, the real gain is about 1,800 a year. Jo decides to ask for more.
- What would change my mind? If the hours are really 50 a week, not 40. Jo asks to speak to someone in the team, who says 45 is normal.
- Frames: "I'd lose my friends here" (loss) and "I'd gain experience I can't get here" (gain). Both are real; Jo lists them side by side.
- Pre-mortem: "It failed because I burned out and had no one nearby." Fix: agree a start date that allows a visit home every month.
Jo still takes the job, but after negotiating a higher offer, a realistic budget and a plan for the biggest risk.
Common mistake
Using the checklist only to justify a decision you have already made. If every answer conveniently supports your first choice, go back to question 4 and look harder for evidence against it, or ask someone who disagrees to answer the questions with you.
Key terms
- inside view
- planning from your own case and plan, imagining it going well
- outside view
- starting from how similar cases went for others
- reference class
- the group of similar past cases you compare with
- planning fallacy
- underestimating how long and how much a plan will take, even knowing past plans overran
- pre-mortem
- imagining a decision has failed and listing why, before you commit
- decision journal
- a written record of a decision, your reasons and what you expect, to review later
Practise the key terms
Tap a card to turn it over. 6 cards.
| Front | Back |
|---|---|
| inside view | planning from your own case and plan, imagining it going well |
| outside view | starting from how similar cases went for others |
| reference class | the group of similar past cases you compare with |
| planning fallacy | underestimating how long and how much a plan will take, even knowing past plans overran |
| pre-mortem | imagining a decision has failed and listing why, before you commit |
| decision journal | a written record of a decision, your reasons and what you expect, to review later |
Practice
Build the sentence
Put the steps of a pre-mortem in order.
Show answer
Describe the plan you're about to commit to Imagine it's a year later and it has failed badly List every reason it might have failed Change the plan to deal with the biggest reasons. Imagining failure as already having happened makes the reasons easier to find, so you can fix them before you start.
Quick quiz
Tap an answer to check it.
In Buehler, Griffin and Ross's study, what share of students finished their thesis by the date they predicted?
- Most overran
- Fewer than half finished on time
Show answer
About 30%. On average they predicted about 34 days and took about 56.
Which checklist question best guards against confirmation bias?
- That guards against narrow framing
- That guards against anchoring
Show answer
What would change my mind, and have I looked for it?. Deciding what would count against you, then looking for it, is the defence against confirmation bias.
Why write down your decision and reasons?
- The point is to learn, not to win
Show answer
So you can later check how good your judgement was, without memory rewriting it. Memory is rebuilt over time; a written record shows what you actually thought.
A friend has filled in the checklist and every answer supports what they wanted to do anyway. What should they do?
- A checklist used only to justify a choice catches nothing
Show answer
Go back to the "what would change my mind" question, or ask someone who disagrees to work through it with them. The checklist works only if it is allowed to find problems.
The other view
You may have heard that it is best to decide big, complex choices by "not thinking about them" for a while, letting your unconscious work them out. A well-known 2006 study claimed this, but later studies, including a large attempt to repeat it (Nieuwenstein and colleagues, 2015), did not find the advantage. Taking a break before a big decision can still help you cool down after a sales pitch or an argument, but it is not a substitute for working through the questions.
In short
- Knowing about biases isn't enough; a short routine catches them.
- The outside view (how did similar cases go?) corrects the planning fallacy: students predicted about 34 days for their thesis and took about 56.
- A pre-mortem imagines the decision has failed and lists why, before you commit.
- The checklist: three options; outside view; where the numbers came from; what would change your mind; both frames; pre-mortem.
- Write the decision and your reasons down, and review them later.
Mastery check
Answer without looking back. Score 80% or more and the lesson is marked done. Your result is kept only in this browser.
Check yourself
Answer in your head first, then open the answer. Nothing is saved.
What is the planning fallacy?
Show answer
Underestimating how long and how much a plan will take, even when you know similar plans have overrun before.
How do you run a pre-mortem?
Show answer
Imagine it is some time later and the decision or plan has failed badly, list all the reasons why, then change the plan to deal with the biggest ones.
Name three questions from the decision checklist.
Show answer
Any three of: what are at least three options; how did similar decisions go for others; where did my numbers come from; what would change my mind; how does it look as a gain and as a loss; why might it have failed a year from now.
Further reading
- Buehler, R., Griffin, D., & Ross, M. (1994). Exploring the "planning fallacy": Why people underestimate their task completion times. Journal of Personality and Social Psychology, 67(3), 366–381.
- Klein, G. (2007). Performing a project premortem. Harvard Business Review, 85(9), 18–19.
- Mitchell, D. J., Russo, J. E., & Pennington, N. (1989). Back to the future: Temporal perspective in the explanation of events. Journal of Behavioral Decision Making, 2(1), 25–38.
- Kahneman, D., Lovallo, D., & Sibony, O. (2011). Before you make that big decision. Harvard Business Review, 89(6), 50–60.
- Nieuwenstein, M. R., et al. (2015). On making the right choice: A meta-analysis and large-scale replication attempt of the unconscious thought advantage. Judgment and Decision Making, 10(1), 1–17.
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