Stock analysis evaluates a company's shares using business fundamentals, valuation, market data, and models to test investment assumptions and risks.
Stock analysis is the evaluation of a company’s shares using financial information, market data, and assumptions about future performance. It can examine what the business is worth, how its shares trade, or whether a proposed investment rule holds up to testing. Those are different questions, and no single ratio answers all of them.
Investors and analysts use the work to compare companies, challenge forecasts, and identify risks that a quoted share price does not reveal. Analysis can support a decision, but it cannot establish that a stock will rise or that it suits a particular investor.
| Approach | Main question | Typical inputs and output | Important limit |
|---|---|---|---|
| Fundamental analysis | What financial performance could justify the share price? | Business economics, financial statements, forecasts, and an estimated value range | A valuation depends on assumptions about future cash flows and risk |
| Technical analysis | What patterns appear in price and trading activity? | Prices, volume, trends, and specified trading signals | A chart signal is not an estimate of the business’s intrinsic value |
| Quantitative analysis | Can a defined numerical rule compare or explain stocks consistently? | Financial ratios, market data, statistical models, and ranked or tested results | A model can fit past observations without working on new data |
CFA Institute distinguishes fundamental analysis of the economy, industry, and company from technical analysis of market data. Model choice and judgment remain important in valuation. See its equity valuation overview.
These approaches are not mutually exclusive. A numerical screen can use fundamental earnings data and technical price trends. However, three indicators calculated from the same price history should not automatically count as three independent confirmations.
An event study answers a narrower, retrospective question: how did returns around specified news differ from a model-based benchmark? That result is not itself a valuation or a forecast.
Consider two fictional companies at the same valuation date. All amounts are in U.S. dollars. Earnings cover the same completed year and are attributable to common shareholders. Each company has one common share class, no preferred shares or potentially dilutive securities, and an unchanged share count throughout that year and at the valuation date.
| Measure | Company A | Company B |
|---|---|---|
| Price per share | $10 | $100 |
| Common shares outstanding | 100 million | 5 million |
| Annual common earnings | $50 million | $50 million |
| Earnings per share | $0.50 | $10.00 |
| Trailing P/E | 20 times | 10 times |
| Equity market capitalization | $1,000 million | $500 million |
For Company A, earnings per share are $50 million divided by 100 million shares, or $0.50. Dividing its $10 price by $0.50 produces a trailing price-to-earnings ratio of 20. Its market capitalization is $10 multiplied by 100 million shares, or $1 billion.
For Company B, $50 million divided by 5 million shares produces $10 of EPS. Its $100 price represents 10 times earnings, while its market capitalization is $500 million.
Company A has the lower unit price but the higher price relative to the same amount of past annual earnings. Buying all its common equity at the quoted price would cost twice as much as Company B’s, before any transaction costs or price impact.
This does not establish that Company B is undervalued or a better investment. Its future earnings could be less sustainable, its debt burden higher, or its growth prospects weaker. Those differences are deliberately absent from the example.
Now assume Company A’s next-year common earnings are forecast to fall to $25 million. Keep its 100 million shares and $10 market price unchanged.
| Company A earnings basis | Annual common earnings | EPS | P/E at $10 |
|---|---|---|---|
| Completed year, reported | $50 million | $0.50 | 20 times |
| Next year, hypothetical forecast | $25 million | $0.25 | 40 times |
The trailing multiple remains 20 because the reported year has not changed. The forecast-based multiple is 40 because $10 divided by projected EPS of $0.25 equals 40.
A screen showing only trailing P/E would miss this forecast change. Conversely, the projected decline might not occur. The next analytical task is to investigate the assumptions behind the $25 million forecast, not treat either multiple as a buy or sell instruction.
A useful comparison records the price date, earnings period, currency, and share-count basis. The constant share counts above make the arithmetic simple; real companies may issue or repurchase shares during the year. Basic EPS uses a weighted-average common share count, while market capitalization uses shares outstanding at the valuation date. Diluted EPS requires additional adjustments.
For U.S. public companies, financial statements, footnotes, risk factors, and management’s discussion in Form 10-K or 10-Q provide starting evidence. The SEC’s guide to reading these filings explains their structure. Other jurisdictions use different reports.
Follow a surprising ratio back to its inputs:
A comparison of two multiples is weaker when their denominators measure different things.
Backtesting applies a specified rule to historical data. An attractive result can be distorted by information unavailable at the test date, omission of failed stocks, or repeated tuning to the same sample.
Before interpreting a simulation, examine point-in-time data, the original stock universe, transaction-cost assumptions, and results on data not used to design the rule. Repeatedly revising a strategy after seeing its test results weakens the independence of that test. CFA Institute’s Investment Model Validation discusses these risks and validation methods.
A practical warning sign is a strategy description that cannot specify its selection rule until after the winning stocks are known. Historical explanations can sound convincing without having been usable beforehand.
This explanation is educational, not personalized investment advice. Valuation errors, changing business conditions, illiquidity, and market losses remain possible even after careful research.