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Managing Type 1 and Type 2 Errors in Stock Investing

13 Mins 17 Nov 2023 0 COMMENT

Stock investing is a delicate balance between making informed decisions and avoiding costly mistakes. Two critical errors that investors often encounter are Type 1 and Type 2 errors. Understanding and managing these errors is essential for building a successful investment portfolio. In this comprehensive reading, we will explore what Type 1 and Type 2 errors are, their implications in stock investing, and strategies to minimize their impact.

What are Type 1 and Type 2 Errors?

Before delving into their relevance in stock investing, let's define Type 1 and Type 2 errors:

  1. Type 1 Error (False Positive): This error occurs when an investor believes that a stock or investment opportunity is attractive when, in reality, it is not. In other words, you make an incorrect positive judgment.
  2. Type 2 Error (False Negative): Conversely, a Type 2 error takes place when an investor overlooks a potentially excellent investment opportunity, considering it unfavorable when it could have been a lucrative choice. In this case, you make an incorrect negative judgment.

Implications in Stock Investing

Understanding Type 1 and Type 2 errors in the context of stock investing is crucial because they can significantly impact your investment outcomes:

Type 1 Error (False Positive)

Loss of Capital: Investing in a stock that turns out to be a false positive can lead to financial losses. These losses can erode your portfolio's value and hinder your overall financial goals. 

Missed Opportunities: The resources allocated to a false positive could have been invested elsewhere, missing out on potentially more profitable opportunities. 

Type 2 Error (False Negative) 

Missed Gains: Failing to recognize a promising investment may result in missed gains. The stock you overlooked could have delivered substantial returns, but you missed out because you considered it unfavorably. 

Underperforming Portfolio: Missing too many false negatives in your portfolio can lead to underperformance, as you miss out on investments that could boost your returns. 

Which is more critical, Type 1 or Type 2 error? 

To illustrate this point, let's consider an example from the book "What I Learned About Investing From Darwin". Imagine that there are 4000 stocks in a given market, of which 1000 are good investments and 3000 are not. Suppose that an investor claims to make correct investment decisions 80% of the time. This means that when presented with opportunities to invest in good stocks, the investor has an 80% chance of making the right decision (20% of the Type 2 error). 

In other words, when faced with bad investment options, he rejects 80% of the bad ones but still chooses 20%, where he makes no profit (20% of the Type 1 error). This means he has a 20% chance of committing both Type 1 and Type 2 errors. Due to the 20% Type 2 error, he would only pick 800 companies out of the 1000 good ones. Furthermore, because of the 20% Type 1 error, he would also select 20% of the 3000 bad investments, which would translate to 600 bad stocks. 

What will be his success rate in this scenario where he has a 20% strike rate of Type 1 and 2 errors? It is not 80%. The answer is 57%. Surprised! Let's see how. 

The total number of stocks he chose was 1400, out of which only 800 were good. Therefore, his success rate was 57% (800/1400). 

Let's see how the success rate changes if he improves Type 1 and 2 errors. The table below shows the results, assuming 1000 good stocks and 3000 bad stocks. 

Type 1 error

No. of bad stocks chosen

Type 2 error

No of good stocks chosen

Success rate





800/1400 = 57%





800/1100 = 73%





900/1500 = 60%

You can observe that reducing the Type 1 error by 10% increases the success rate by 16% while reducing the Type 2 error by the same percentage only increases it by 3%. 

Even if both errors are reduced to 10%, the success rate increases to 75%, which is 2% higher for the investor focusing only on reducing Type 1 errors. This means that the success rate can be dramatically improved by reducing the chances of making a bad investment or Type 1 error. 

Source: From the book titled - What I Learned About Investing From Darwin 

Strategies to Minimize Type 1 Errors 

Minimizing Type 1 errors is essential to protect your capital and make informed investment decisions:

1. Thorough Research 

Conduct thorough fundamental analysis, examining a company's financials, industry trends, and competitive positioning. This reduces the chances of investing in fundamentally weak stocks.

2. Spread Risk via Diversification 

Diversify your portfolio across different sectors and asset classes. By doing so, the impact of a single false positive on your overall portfolio is limited.

3. Set Entry and Exit Criteria

You should define clear entry and exit criteria for your investments. Stick to these criteria, ensuring that you only invest when the fundamentals align with your strategy.

4. Risk Management 

Implement stop-loss orders to limit potential losses. If a stock's price falls below a certain threshold, you automatically sell, minimizing losses from false positives. 

Strategies to Minimize Type 2 Errors 

Minimizing Type 2 errors is also important to maximize your portfolio's potential, but you need to be cautious not to make any poor investment decisions, as that can reduce your portfolio performance drastically, as we have seen in the above example.

1. Stay Informed

Stay up-to-date with market trends, economic developments, and industry news. Regularly review your investment strategy to identify any overlooked opportunities.

2. Expand Your Research

Consider investments that may not be in your immediate comfort zone. Explore different industries, asset classes, and geographic regions.

3. Use Screening Tools

Leverage stock screening tools that allow you to filter stocks based on various criteria, helping you identify potentially promising investments.

4. Seek Professional Advice

Consult with financial advisors or experts who can provide valuable insights and prevent you from missing out on opportunities.

Striking the Right Balance

Balancing efforts to minimize Type 1 and Type 2 errors is essential. Here are some strategies for striking the right balance: 

1. Quantify Risk Tolerance   

Understand your risk tolerance, and align your investments accordingly. Higher risk tolerance may allow you to explore more opportunities, reducing Type 2 errors. 

2. Regular Portfolio Review 

Review your portfolio regularly to identify and rectify potential Type 1 errors. Re-evaluate your investment thesis and exit positions if fundamentals deteriorate. 

3. Risk-Reward Analysis 

Consider the trade-offs between Type 1 and Type 2 errors. Understand that a more risk-averse approach may lead to more Type 2 errors but also minimize Type 1 errors. 

Example: Balancing Type 1 and Type 2 Errors 

Imagine an Indian stock investor, Raj, who is considering investing in the technology sector. He identifies two companies: Company A and Company B. 

Company A: Raj has done thorough research on Company A, and all indicators suggest that it's a strong investment. He decides to invest a significant portion of his portfolio in this stock. 

Company B: On the other hand, Raj has limited information on Company B. He is unsure about its potential, so he decides to pass on this opportunity. 

In this scenario: 

- If Company A performs well, Raj avoids a Type 2 error (false negative) but risks a Type 1 error (false positive). 

- If Company B turns out to be a lucrative investment, Raj avoids a Type 1 error (false positive) but falls victim to a Type 2 error (false negative). 

To strike a balance, Raj should diversify his investments and conduct further research on Company B while still investing in Company A. This way, he reduces the impact of Type 1 and Type 2 errors on his portfolio. 


Managing Type 1 and Type 2 errors in stock investing is a complex yet critical task. Striking the right balance between avoiding false positives and false negatives is essential for building a successful investment portfolio. 

By conducting thorough research, diversifying your investments, setting clear criteria, staying informed, expanding your research scope, using screening tools, seeking professional advice, and periodically reviewing your portfolio, you can navigate the complexities of stock investing and make well-informed decisions. 

Remember that risk is inherent in investing, and both types of errors are inevitable. What matters is how you manage and minimize their impact to maximize your chances of achieving your financial goals in the ever-evolving world of stock markets.