Question

Which of the following cannot be the probability of any event?

• A. 1
• B. $-1$
• C. $\tfrac{1}{2}$
• D. $\tfrac{1}{3}$

Hint:

Always remember: Probability values must lie within $[0,1]$. Any negative or greater-than-one value is invalid.

Answer 1

The Correct Option is B

Step 1: Probability range
The probability of any event always lies between $0$ and $1$ (inclusive). That is:
\[ 0 \leq P(E) \leq 1 \]

Step 2: Checking the options
- Option (A) $1$: Valid probability (sure event).
- Option (B) $-1$: Not possible, since probability cannot be negative.
- Option (C) $\tfrac{1}{2}$: Possible, represents 50% chance.
- Option (D) $\tfrac{1}{3}$: Possible, represents a valid fraction.

Step 3: Conclusion
Since probability cannot be negative, $-1$ is not possible.
The correct answer is option (B).