The number of hours per day a college student spends on homework has a mean of 6 hours and a standard deviation of 1.25 hours. Yesterday she spent 3 hours on homework. How many standard deviations from the
Mean is that? Round your answer to two decimal places.
A) 2.40 standard deviations below the mean
B) 1.20 standard deviations below the mean
C) 1.20 standard deviations above the mean
D) 2.40 standard deviations above the mean

Question

Quizplus · Accepted Answer

To find how many standard deviations from the mean the student's 3 hours of homework is, we use the z-score formula: z = (x - μ) / σ where x is the given value (3 hours), μ is the mean (6 hours), and σ is the standard deviation (1.25 hours). 
Plugging in the values, we get z = (3 - 6) / 1.25 = -2.40. 
Since the z-score is negative, we know that the value is below the mean. Therefore, the answer is choice A) 2.40 standard deviations below the mean.

The Number of Hours Per Day a College Student Spends