False  Positive and False Negative: Part I

This topic is really rather important, since we make all sorts of decisions based on what we observe, on research findings, on test results, and so on.  If we don't know about these two possible results of our observations, etc., we can make decisions without considering the full implications.

So in case you don't know what these are, here's another story to help explain, one that highlights how important it is to know about False Positives and False Negatives.

Mistakes happen, even when we try our best

Well, were dealing with reality again.  Robert and Harold went through some medical testing in order to find out if there was some sort of illness causing their symptoms.  Now, the results each received could have been true (they could have shown reality), or false (they could have failed to show reality). 

And as it happened, for this example, the test results were actually wrong (false) for both men.  They did not provide valid conclusions about the real health of either.  And that's what can happen whenever we try to know reality.  We can make a mistake.  We do all we can to prevent that, but it can happen.

False Positive:

Robert's results were a false positive.  They said he had leukemia, when he didn't  That's what a false positive is, saying something is true (the test said Robert truly had leukemia) when it is not true (he didn't really have leukemia).

False Negative:

Harold's results were a false negative.  They said he didn't have leukemia when he did.  That's what a false negative is, saying something is NOT true (the test said Harold truly did not have leukemia), when it is not false (he really did have leukemia).

Robert went through unnecessary and arduous treatment, while Harold failed to receive treatment he needed.

Robert' lived.  Harold died.

Again we ask: Who would you rather be, Robert, or Harold?

Sure, what everyone would prefer is to be neither.  We would wish to avoid both false positives and false negatives.  We would want true positives, or true negatives.  Unfortunately, that's not always possible. 

So, since there can always be some errors in medical test results, which would you prefer, being told you were sick, when you're really not, or being told your not sick, when you really are?  If these were the only two choices, would you prefer to go thorough unnecessary and grueling treatment and live, or receive no treatment and die? 

In other words, which error would you be most willing to make, a False Positive, or a False Negative?

Well, for the most part it depends on context...

In some contexts we're more willing to make a False Positive, while in others we're more willing to make a False Negative.  For example:

Medicine: When it comes to medical results, especially when a possible fatal illness is involved, most would prefer a possible error to be a  false positive (saying we have an illness when we don't) rather than a false negative (saying we don't have an illness when we do).  Generally, we're not keen on dying from a failure to diagnose a fatal illness.

Courts: Interestingly, when it comes to someone being tried for murder, we tend to prefer to let a guilty person go free (a false negative--finding a guilty person not guilty) to a false positive (finding an innocent person guilty), since in many states we execute people convicted of murderer.  Generally, we're not keen on executing innocent people. Or at least that used to be our preference.

 If you'd like to know more about false positives and false negatives

 To read about a couple ways of thinking (divergent and convergent)

 To read about causality

 To read about who likes it when people are ignorant, or stupid

 To go the Articles Page.