Original practice · fully worked
Original variant: intersect two component-test events
Three labeled components are tested once, and each outcome is written as a three-letter P/F string in test order. Let A be the event that the first component passes, and let B be the event that exactly two components pass. Which set of outcome strings is A intersect B?
- A
{PPP} - B
{PPF, PFP} - C
{PPF, PFP, FPP} - D
{PFF} - E
{PPP, PPF, PFP, PFF}
Answer and calculation
Event B contains the three strings with exactly two passes. Keeping only those whose first symbol is P leaves PPF and PFP, choice B.
Setup
Setup
List the outcomes satisfying the exact-two-pass requirement.
B={PPF,PFP,FPP} Model
Model
List the outcomes whose first component passes.
A={PPP,PPF,PFP,PFF} Compute
Compute
Retain the strings appearing in both sets.
A∩B={PPF,PFP} Answer
Answer
Exactly two outcome strings satisfy both conditions.
{PPF,PFP}(B)