Question

Exam scores of a very easy test follow a negatively skewed distribution. These scores have µ = 50 and σ = 15. Eric got 61 on this exam. Which of the following statements must be correct?

Question 50.5 pts

Exam scores of a very easy test follow a negatively skewed distribution. These scores have µ = 50 and σ = 15. Eric got 61 on this exam. Which of the following statements must be correct?

(A) 50% of the class got scores above 50.

(B) Eric did better than 76.73% of his classmates.

(C) Eric did better than 73% of his classmates

(D) there is not enough information to calculate probabilities as we don’t have a normal distribution

Answer 1

We can work with the probabilities if the curve looks like this:

i.e A normal distribution which is a symmetric curve.
However, in this case the distribution is negatively skewed( left skewed ) like this:

Here the curve is not symmetric hence we can't calculate the percentile of Eric's score.

Ans. (D) there is not enough information to calculate probabilities as we don't have a normal distribution.