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The positive predictive value (PPV), or precision, is defined as = + = where a "true positive" is the event that the test makes a positive prediction, and the subject has a positive result under the gold standard, and a "false positive" is the event that the test makes a positive prediction, and the subject has a negative result under the gold standard.
A positive net present value indicates that the projected earnings generated by a project or investment (in present dollars) exceeds the anticipated costs (also in present dollars). This concept is the basis for the Net Present Value Rule, which dictates that the only investments that should be made are those with positive NPVs.
In clinical practice, post-test probabilities are often just estimated or even guessed. This is usually acceptable in the finding of a pathognomonic sign or symptom, in which case it is almost certain that the target condition is present; or in the absence of finding a sine qua non sign or symptom, in which case it is almost certain that the target condition is absent.
The easiest way to calculate the net present value of an investment is using an online NPV calculator. You can also make these calculations in Excel. You can also make these calculations in Excel.
PPV is best understood by comparison to two other approaches where a penalty is applied for risk: The risk-adjusted rate of return applies a risk-penalty by increasing the discount rate when calculating the Net Present Value (NPV); The certainty equivalent approach does this by adjusting the cash-flow numerators of the NPV formula.
The Positive predictive value (PPV) of a test is the proportion of persons who are actually positive out of all those testing positive, and can be calculated from a sample as: PPV = True positive / Tested positive. If sensitivity, specificity, and prevalence are known, PPV can be calculated using Bayes' theorem.
The convenient and intuitively understood term specificity in this research area has been frequently used with the mathematical formula for precision and recall as defined in biostatistics. The pair of thus defined specificity (as positive predictive value) and sensitivity (true positive rate) represent major parameters characterizing the ...
Calculating the net present value, , of a stream of cash flows consists of discounting each cash flow to the present, using the present value factor and the appropriate number of compounding periods, and combining these values. [1]