H3

Consider old computers. When starting this, you will often get a blue screen, which we refer to as Event B. A hardware error, event H, or a software error, event S, can be responsible for this. The following probabilities apply here:

P(B | H S )=0,5, P(B | H S)=0,3, P(B | H S)=0,9, P(B | H S)=0.

( is the complement of an event.)

From experience you know that 30% of all computers have no fault, 25% only a hardware fault, 25% only a software fault and the remaining computers have both a hardware and a software fault.

i) Calculate P(B)

ii) Calculate P(H | B)