If two options are acceptable and you have no important reason to prefer either, a coin flip can finish the choice. Assign one option to heads, the other to tails, and toss once.
The important work happens before the toss: deciding which options belong in it. Randomness can settle a tie. It cannot check your budget, make an unsafe option safe, or tell you which outcome will turn out better.
First, decide whether either result would be acceptable
A coin flip is reasonable for a modest choice when you know enough about both options, can accept their likely downsides, and are willing to proceed with either result.
That might mean choosing between two familiar walking routes, two notebooks with the same useful specifications, or two activities that everyone involved has agreed would be fine.
Remove unacceptable options first. If one restaurant cannot meet a dietary requirement or one activity exceeds your budget, do not give it a chance to win. The fact that you could veto it afterward does not make it a useful candidate.
Check other people's agreement, too. “I flipped a coin” is not a substitute for consent when the result affects their evening, time, or money.
You can also choose without randomizing. A small, unremarkable preference is enough reason to select an option. The coin is available when you want a tie-breaker; you do not have to use it to prove you are impartial.
How to make a fair random choice
For an ideal fair coin, heads and tails each have a 50% chance. Assigning one option to each side gives the options equal chances of selection. It does not mean they have equal merit or equal chances of making you happy.
Use this procedure:
- Write two distinct, acceptable options.
- Assign heads to one and tails to the other before tossing.
- Decide that you will use one toss. If someone else is involved, agree on the assignments and rule together.
- Toss the coin and read the result without changing which option it represents.
- Carry out the selected option, unless you identify a real reason it is no longer acceptable.
A physical toss is a practical everyday approximation to the ideal. It is not a guarantee of exact equal odds under every tossing technique: research has found a slight tendency for tossed coins to finish with their starting side up. You can randomize which side starts facing up, or use a random selector that explicitly gives each option equal weight. See the original coin-toss research.
For more than two options, a single toss cannot give each its own equally likely outcome. Use an equal-weight list picker, or write one option on each of equally sized slips, fold them, mix them, and draw one. Putting two options on heads and one on tails does not give all three equal chances.
What the toss accomplishes
The coin supplies a selection rule that does not depend on finding another advantage. That can be all you need.
Suppose both notebooks meet your requirements, cost the same, and appeal to you equally. Choosing one at random lets you get on with using it. The choice does not become more valid if you invent a story about why that cover was destined for you.
A toss also makes a hypothetical outcome concrete enough to consider: “All right, this is the one I would choose.” You may notice a reaction. You may feel nothing much at all. Neither response prevents you from making an ordinary choice.
Is disappointment a clue about what you want?
It can be a useful prompt to inspect the decision. It is not a reliable test of a hidden true preference.
In 2019 experiments involving hypothetical menu choices, participants reported stronger feelings when a random device suggested an option. That concerns reported reactions in a particular setting, rather than proof of better real-world outcomes. Read Jaffé and colleagues' study.
A later paper tested choices between art posters across three studies. Reactions to the coin's result reflected earlier attractiveness ratings, but the researchers did not find reliable evidence that using a coin improved alignment between those prior ratings and final choices. Read Jaffé and Greifeneder's study.
If you dislike the result, ask what specifically bothers you. “I don't want to spend that much tonight” identifies a constraint. “I'd rather do the other activity” states a preference you are allowed to act on. Neither requires an explanation about your subconscious.
A brief reaction also cannot establish what you will prefer tomorrow or how the experience will go. Treat it as something to consider alongside your reasons.
A worked example: choosing a walking route
Imagine this illustrative situation: you have time for either of two familiar walks. Both fit your available time, both are suitable for today's conditions, and you would enjoy either. You have no particular destination to reach.
You assign heads to the park loop and tails to the neighborhood loop. You agree with yourself to use one toss. It lands tails, so you put on your shoes and take the neighborhood loop.
That is a complete use of the method. You do not need a revealing emotional moment.
Now consider a variation. Tails lands and you think, “Actually, I want to see the trees today.” You can choose the park instead. You have used the result as a prompt and then made the choice yourself. Be clear about that distinction, especially if another person agreed to follow the toss.
If you notice that one route is unsuitable today, remove it. A newly recognized constraint is a reason to change the decision, not a reason to pretend both options are still acceptable and keep tossing.
Why repeated flips change the exercise
If you keep tossing until your favorite wins, you are no longer following a one-toss random choice. You are choosing which result to accept.
That does not make the preference wrong. It does mean you can stop tossing and own the selection. With another person, explain the change and reach agreement rather than presenting the eventual result as the fair outcome you originally promised.
Deciding on “best of three” in advance is a different rule. Changing to it after an unwelcome first result changes the agreement. For a small personal tie, one toss is usually the simpler procedure.
When to put the coin away
Avoid randomness when an important requirement remains unchecked, one option carries an unacceptable downside, or the choice affects someone who has not agreed to the method.
Medical, legal, major financial, and hard-to-reverse decisions need assessment and advice appropriate to their consequences. A coin cannot supply missing expertise or remove responsibility for the result.
If you need to choose between two good options with meaningful trade-offs, compare those trade-offs first. You might find a priority that makes the decision clear.
If you are simply left with two acceptable ways to spend a small part of your day, randomness can be perfectly adequate. Name the options, assign the sides, toss once, and take the next step.