Headwater Box Plot Questions

Question
What is the significance of the zero line on this plot? (Choose the best answer.)
The correct answer is c.
Question
Which box plot shows the middle 50% of the forecast distribution intersecting the zero line? (Choose the best answer.)
The correct answer is b.
Question
Which box plot shows that none of the ensemble members match the forecast? (Choose the best answer.)
The correct answer is a.
Question
Which box plot shows an overforecast bias? (Choose the best answer.)
The correct answer is a.
Question
What does box plot 3 tell us about how the observation matches the ensemble forecasts? (Choose the best answer.)
The correct answer is c.