Final answer:
Technician A is correct that the cylinder causing the biggest RPM drop during a power balance test is the weak cylinder. Technician B is incorrect that grounding out one spark plug wire indicates a weak or dead cylinder.
Step-by-step explanation:
Technician A is correct. During a power balance test, the cylinder that causes the biggest RPM drop is typically the weak cylinder. This is because a weak cylinder will produce less power and therefore contribute less to the overall engine speed.
Technician B is incorrect. If one spark plug wire is grounded out and the engine speed does not drop, it does not necessarily indicate a weak or dead cylinder. Other factors such as the condition of the spark plug or fuel delivery system can also affect engine speed.