Quantitative Literacy Practice Exam 2026 – Comprehensive Preparation Guide

To calculate the z-score for a given score, you can use the formula:

\[ z = \frac{(X - \mu)}{\sigma} \]

where:

- \( X \) is the score in question (in this case, 85),

- \( \mu \) is the mean (average) of the data (which is 80), and

- \( \sigma \) is the standard deviation (which is 10).

By plugging in the values into the formula, you perform the following calculation:

1. Subtract the mean from the score: \( 85 - 80 = 5 \).

2. Divide this result by the standard deviation: \( \frac{5}{10} = 0.5 \).

Thus, the z-score for a score of 85 is 0.5, meaning the score is half a standard deviation above the average.

The correct answer indicates how far the score is from the mean relative to the standard deviation, capturing the concept of standardized measurements in statistics.