In a math aptitude test, students scores are found to be normally distributed having mean as 45 and standard deviation 5. What percent of students scored more than the mean score?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 50%
A normal curve is symmetric about its mean, so exactly half of the total area lies on each side of the mean.
In terms of the standard normal variable,
\( \displaystyle Z=\frac{X-\mu}{\sigma}=\frac{45-45}{5}=0 \)
\( P(X\gt 45)=P(Z\gt 0)=0.5 \)
So 50% of the students scored more than the mean score. The standard deviation 5 does not affect this.