In a certain breed of cattle, the length of gestation has a mean of 284 days and a standard deviation is 5 point 5 days. One length of gestation had a z -score of negative 1 point 7 0 Which of the following sentences best interprets this z -score?
Answer
A
The length of this gestation period was shorter than the mean length of gestation periods by 1 point 7 days.
B
The length of this gestation period was longer than the mean length of gestation periods by 1 point 7 standard deviations.
C
The length of this gestation period was longer than the mean length of gestation periods by 1 point 7 days.
D
The length of this gestation period was shorter than the mean length of gestation periods by 1 point 7 standard deviations.
Explanation
A z-score tells how many standard deviations a value is from the mean. The negative sign means this gestation period was below the mean, and 1.70 gives the distance in standard deviations—not days. Therefore, it was shorter than the mean by 1.7 standard deviations.
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