Respuesta :
Answer:
(c) Probability that a failure is due to loose keys = 0.2376
(d) Probability that a failure is due to improperly connected or poorly welded wires = 0.078
Step-by-step explanation:
The Whole probability scenario is given for Computer Keyboard failures.
(a) Let F be the event of failure due to faulty electrical connects, P(F) = 0.12
 M be the event of failure due to mechanical defects, P(M) = 0.88
 LK be the event of mechanical defect due to loose keys, P(LK/M) = 0.27
 IA be the event of mechanical defect due to improper assembly, P(IA/M)  =0.73
 DW be the event of electrical connects due to defective wires,P(DW/F) = 0.35
 IC be the event of electrical connects due to improper connections,
 P(IC/F) = 0.13 .
PWW be the event of electrical connects due to poorly welded wires,
 P(PWW/F) = 0.52
(b) Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Keyboard failures
               /        \
      Faulty electrical connects        Mechanical Defects     Â
           P(F) = 0.12                       P(M) = 0.88
    /       |       \          /       \
Defective wires  Improper     Poorly          Loose Keys    Improper
P(DW/F)=0.35  Connections  Welded wires    P(LK/M)=0.27  Assembly
              P(IC/F)=0.13   P(PWW/F)=0.52               P(IA/M)=0.73       Â
This is the required tree diagram.
(c) Probability that a failure is due to loose keys is given by:
 P(LK) =P(LK/M) * P(M) {This means mechanical failure is due to loose Â
                        keys}
  P(LK) = 0.27 * 0.88 = 0.2376 .
(d) Probability that a failure is due to improperly connected or poorly welded
   wires is given by P(IC [tex]\bigcup[/tex] PWW) ;
 P(IC [tex]\bigcup[/tex] PWW) = P(IC) + P(PWW) - P(IC [tex]\bigcap[/tex] PWW) { Here P(IC [tex]\bigcap[/tex] PWW) = 0 }
 P(IC) = P(IC/F) * P(F)  = 0.13 * 0.12 = 0.0156
 P(PWW) = P(PWW/F) * P(F) = 0.52 * 0.13 = 0.0676
Therefore, P(IC [tex]\bigcup[/tex] PWW) = 0.0156 + 0.0676 - 0 = 0.078 .