Assume that your class took an exam last week and the mean and standard deviation of the exam were 85 and 5, respectively. Your instructor told you that 30 percent of the students had a score of 90 or above. You would probably
A) think that your instructor was out of her mind.
B) decide that your score of 80 would probably fall in the failing range.
C) conclude that the scores were not normally distributed.
D) conclude that such a set of scores could not possibly happen.

Question

Quizplus · Accepted Answer

If the normal distribution is assumed, we can use the z-score formula to find the proportion of students who scored 90 or above. However, if the actual proportion is significantly different from the expected proportion based on the normal distribution, it suggests that the distribution is not normal. Therefore, it is more likely that the scores were not normally distributed and the assumption of normality should be checked. Without further information on the distribution, we cannot draw any conclusions about individual scores.

Assume That Your Class Took an Exam Last Week and the Mean