Sorry, let me rephrase the final sentence of that first paragraph!
----- Original Message -----
From: "Adrian Fogarty" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, March 01, 2006 1:19 AM
Subject: Re: SAH
> My definition of likelihood ratio: well, I was "paraphrasing" really - and
> omitted the denominator! I understand negative likelihood ratio to be
> "the probability of an individual with the condition having a negative
> test - over - the probability of an individual without the condition
> having a negative test". Now, since the latter (the denominator) is very
> close to unity, I have taken the liberty of omitting it for clarity's
> sake. Hence, when I'm told the negative likelihood ratio of CT for SAH is
> 0.02, that tells me that 1 in 50 of patients with a negative scan will
> nonetheless have an SAH.
...that tells me that 1 in 50 SAH patients will have a negative scan.
A subtle point I know, but massive to the statisticians on the list, who
would no doubt pounce on it!
|