<PRE><B>Question 1061648</B>
A certain disease has an incidence rate of 0.5%. If the false 
negative rate is 7% and the false positive rate is 2%, compute 
the probability that a person who tests positive actually has 
the disease.
&lt;pre&gt;
A lot more information is given here than we need to answer
the question.

Note that if&lt;/pre&gt;a person who tests positive actually has the disease.&lt;pre&gt;then the positive test has &lt;u&gt;&lt;b&gt;succeeded&lt;/b&gt;&lt;/u&gt;.

So we are simply asked for the probability that a positive test 
&lt;u&gt;&lt;b&gt;succeeds&lt;/b&gt;&lt;/u&gt;.

We are told that:&lt;/pre&gt;The &lt;u&gt;&lt;b&gt;false&lt;/b&gt;&lt;/u&gt; positive rate is 2%...&lt;pre&gt;That means that the probability that a positive test
&lt;u&gt;&lt;b&gt;fails&lt;/b&gt;&lt;/u&gt; is 2%.

Therefore the probability that a positive test
&lt;u&gt;&lt;b&gt;succeeds&lt;/b&gt;&lt;/u&gt; is 100% - 2% = 98%.

[The other numbers given are unnecessary to answer this, 
for they are about negative tests and what the probability
that a randomly picked person has the disease.]

Edwin&lt;/pre&gt;</PRE>