Final answer:
A claim from a person with poor eyesight does not significantly change the probability of ghosts existing.
Step-by-step explanation:
If you think there's a 5% chance that ghosts exist, and your uncle, who has poor eyesight, says he saw a ghost, it does not significantly change your estimate of the probability of ghosts existing. Your uncle's poor eyesight and previous mistaken identification indicate that his claim may not be accurate or reliable.
One isolated incident does not provide strong evidence to override your initial estimate of a 5% chance of ghosts existing.