The probability tests to detect the presence of hepatitis B:
P (presence)= 0.97 (true) 0.03 (false)
P (absence)= 0.99 (true) 0.01 (false)
P(infected)=0.0055
P(not infected)= 0.9945
To have an incorrect result:
P[infected and false from P(presence)] + P[not infected and false from P(absence)]
=0.00550.03+0.99450.01= 0.01011
The answer is 0.01011