Each of two lamps has probability $0.9$ of working on a particular evening. They share a power sup

Question

Each of two lamps has probability $0.9$ of working on a particular evening. They share a power supply. A pupil calculates the probability that both work as $0.9^2=0.81$. Explain why the given information does not justify this calculation. State an additional assumption that would make it valid.[2]

Accepted Answer

Independence is not established; a shared fault could affect both. The product is valid if the two working events are independent.

Checking an independence assumption

Checking an independence assumption

Solution:

Solution locked