Find the z-score corresponding to the given value and use the z-score to determine whether the value is unusual. Consider a score to be unusual if it is at least three standard deviations above or Below the mean. Round the z-score to one decimal place, if necessary. A test score of 93.4 on a test having a mean of 73 and a standard deviation of 12.
A)1.7; not unusual
B)-1.7; not unusual
C)1.7; unusual
D)20.4; unusual

Question

Find the z-score corresponding to the given value and use the z-score to determine whether the value is unusual. Consider a score to be unusual if it is at least three standard deviations above or Below the mean. Round the z-score to one decimal place, if necessary. A test score of 93.4 on a test having a mean of 73 and a standard deviation of 12. 
A)1.7; not unusual
B)-1.7; not unusual
C)1.7; unusual
D)20.4; unusual

Quizplus · Accepted Answer

The z-score is calculated as (X - μ) / σ = (93.4 - 73) / 12 = 20.4 / 12 = 1.7. Since the z-score is less than 3, it is not considered unusual.

Find the Z-Score Corresponding to the Given Value and Use