From: skybuck2000@hotmail.com   
      
   Corona Update 24, Mathematical proof self-tests are only 3% correct, 97% false   
   positives !   
      
   3% of the corona/covid 19 self-tests are correct, 97% are false positives !   
      
   The mathematical proof has been delivered (using Bayes' theorem):   
      
   Roche's corona self-test has a sensitivity of 96.52% and a specificity of   
   99.68%.   
      
   If "C19" stands for the presence of the disease COVID-19 ("corona") and    
   + and − respectively for a positive and negative result of the test, this   
   means:    
      
   sensitivity: P( + | C19 ): 0.9652   
      
   specificity: P( - | not C19): 0.9968   
      
   That seems very high. But if the prevalence is only 1 in 10,000, i.e    
      
   prevalence: P( C19 ): 0.0001   
      
   This implies:   
      
   P( + ) = P( + | C19 ) P( C19 ) + P( + | not C19 ) P ( not C19 ) =   
      
          = 0.9652 x 0.0001 + 0.0032 x 0.9999 = 0.0033   
             
   and   
       
   P( C19 | + ) = ( P( + | C19 ) P( C19 ) ) / P( + ) =   
      
                = ( 0.9652 x 0.0001 ) / 0.0033 = 0.03   
                   
      
   If 10,000 people are tested with this test, including probably 1 infected   
   person,    
   then the infected person will almost certainly get a positive result.    
   But of the 9,999 uninfected people, 32 will get a false positive result.    
   The 9967 people with a negative result are almost certain that they are not   
   infected.    
   But of the 33 with a positive result, only 1 is infected,    
   only it is unknown who that is.    
   So the chance that an individual is actually infected after a positive result    
   is only slightly more than 3% in this scenario.    
   This self-test is therefore of little use to determine whether you are   
   infected with corona,    
   unless the prevalence is around 1% or higher.    
      
   (This information has been known and published since 20 june 2021 !)   
      
   Bye,   
     Skybuck ! =D   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)