Step 02
Level: beginner
Investing is about making decisions under conditions of uncertainty, so good results come from probability and process rather than absolute certainty. If the thinking is wrong, investors can use the right tools but still make poor decisions.
expected value is a weighted average of possible outcomes. A good decision can be lost on a single occasion, and a poor decision can still succeed by luck. What needs to be evaluated is the distribution of outcomes across multiple decisions. When you have a clear frame of mind, you are less susceptible to news, short-term prices or crowd emotions.
In the early stages, the important goal is to survive, learn the right lessons, and not let one big mistake ruin long-term accumulation.
Investing is about making decisions under conditions of uncertainty, so good results come from probability and process rather than absolute certainty.
New investors often look for formulas to choose assets before building their thinking system. This is dangerous because the same information can lead to very different decisions depending on how risks, probabilities, time horizons and capacity limits are understood. The right mindset does not make the market easier, but it helps you respond with more discipline.
expected value is a weighted average of possible outcomes. A good decision can be lost on a single occasion, and a poor decision can still succeed by luck. What needs to be evaluated is the distribution of outcomes across multiple decisions.
A good investment decision must answer four questions: what do you expect to happen, why is that expectation reasonable, if it is wrong, what is the downside, and is this decision consistent with your personal financial goals? If one of the four answers is missing, the decision is still weak.
Before every decision, write at least three scenarios: good, baseline, and bad; assign approximate probabilities and estimate the impact on capital.
It's important to write down your assumptions before taking action. It forces you to turn feelings into testable arguments. Later, whether the result is profit or loss, you still know where you were right, where you were wrong, and what part of the process needs to be improved.
Evaluating a decision only by the final outcome without considering the initial probability.
An investment mistake usually does not appear as an obviously wrong decision. It often comes in the form of a reason that sounds reasonable but is unproven. Therefore, always have a checklist, position-size limit and review schedule so that your decision does not depend entirely on emotions at the time of purchase.
The expected value is calculated by multiplying each outcome by the corresponding probability and then adding it together.
The set of possible outcomes with their relative probabilities.
The mistake of evaluating the quality of a decision based solely on results that have already occurred.
Decisions can be based on data, analysis, rules or emotions. Investors need to know which group they are in before increasing their capital scale.
A decision that is right for a 10-year goal may be wrong for a 6-month goal. The time frame determines the level of volatility that can be tolerated and the evaluation criteria.
Good decisions always have loss limits, reasonable weights and review conditions. If downside is not controlled, expected returns can easily become an illusion.
Application in investment decisions
An investment that has a 60 percent probability of a 20 percent gain and a 40 percent probability of a 10 percent loss has a positive expected value, but can still lose money over a specific period.
Behavioral risks
Evaluating a decision only by the final outcome without considering the initial probability. When this happens repeatedly, investors are more likely to increase risk just when discipline is weakest.
A profitable decision is not always a good decision, and a losing decision is not always a bad one. Evaluate both the process and the initial probabilities.
Without a written buy thesis, it becomes hard to know when the thesis is wrong and easy to rewrite the narrative after prices move.
Evaluating a decision only by the final outcome without considering the initial probability. Position size should increase only after the process has been tested, not after a few favorable outcomes.
Exercise 1 - reflection
Describe a recent investment decision you made and evaluate it from the perspective of probability and expected value thinking.
Exercise 2 - case_study
An investment that has a 60 percent probability of a 20 percent gain and a 40 percent probability of a 10 percent loss has a positive expected value, but can still lose money over a specific period. Identify the decision basis, the main risks, and the downside controls.
Exercise 3 - action_plan
Write a checklist of 5 questions to avoid this mistake in your next investment decision.