The essential point in security analysis is to establish that the value is adequate

Businesses, unlike debt instruments, do not have contractual cash flows.  As a result, they cannot be as precisely valued as bonds.  

Benjamin Graham knew how hard it is to pinpoint the value of businesses and thus of equity securities that represent fractional ownership of those businesses.  In Security Analysis he and Dodd discussed the concept of a range of value.

'The essential point is that security analysis does not seek to determine exactly what is the intrinsic value of a given security.  It needs only to establish that the value is adequate - e.g., to protect a bond or to justify a stock purchase - or else that the value is considerably higher or considerably lower than the market price.  For such purposes an indefinite and approximate measure of the intrinsic value may be sufficient.'

Indeed, Graham frequently performed a calculation known as net working capital per share, a back-of-the-envelope estimate of a company's liquidation value. His use of this rough approximation was a tacit  admission that he was often unable to ascertain a company's value more precisely.

Business value cannot be precisely determined: Be approximately right than be precisely wrong

Many investors insist on affixing exact values to their investments, seeking precision in an imprecise world, but business value cannot be precisely determined.

• Reported book value, earnings, and cash flow are, after all, only the best guesses of accountants who follow a fairly strict set of standards and practices designed more to achieve conformity than to reflect economic value.  
• Projected results are less precise still.  

You cannot appraise the value of your home to the nearest thousand dollars.  Why would it be any easier to place a value on vast and complex businesses?

Not only is business value imprecisely knowable, it also changes over time, fluctuating with numerous macroeconomic, microeconomic, and market-related factors.  So while investors at any given time cannot determine business value with precision, they must nevertheless almost continuously reassess their estimates of value in order to incorporate all known factors that could influence their appraisal.

Any attempt to value businesses with precision will yield values that are precisely inaccurate.  The problem is it is easy to confuse the capability to make precise forecasts with the ability to make accurate ones.