Final answer:
The z-score for Tony's GRE quantitative reasoning score is 0.1250, which indicates that Tony scored above the mean on the GRE quantitative reasoning test.
Step-by-step explanation:
To calculate the z-score for Tony's GRE quantitative reasoning score, we use the formula z = (X - μ) / σ, where X is Tony's score, μ (mu) is the mean score, and σ (sigma) is the standard deviation.
Tony's GRE score, X, is 615. The mean GRE score, μ, is 600, and the standard deviation, σ, is 120.
So, the z-score for Tony's score is:
z = (615 - 600) / 120
z = 15 / 120
z = 0.125
Therefore, to four decimal places, Tony's z-score is 0.1250.
The z-score tells us how many standard deviations Tony's score is from the mean. Since the z-score is positive, we know that Tony scored above the mean for the GRE quantitative reasoning test.