What fraction of drivers who crashed after falling asleep did not detect any signs of drowsiness before crashing?

• A. One third
• B. All of them
• C. Two thirds
• D. One half

Answer: (D)

This question is about interpreting proportions within a specific group: drivers who crashed after falling asleep. It’s asking what fraction did not detect any signs of drowsiness before the crash, meaning they had no warning cues before impact. If the data show that exactly half of these drivers had no detectable signs, then the fraction is one half. That indicates a significant portion crash without realizing they’re drowsy, highlighting why self-awareness isn’t enough and why fatigue-detection systems can be important. The other options would imply different shares (about 33%, all, or about 66%), which aren’t what the data describe. So the correct fraction is one half.