The class average on a math test was 75.5 and the standard deviation was 4.2. Find the z-score for a test score of 81
z-score = (81 - 75.5)/4.2 = appr 1.30
To find the z-score of a test score, we need to use the formula:
Z = (X - μ) / σ
Where:
Z is the z-score,
X is the test score,
μ is the mean (class average),
and σ is the standard deviation.
Given:
X = 81 (test score)
μ = 75.5 (class average)
σ = 4.2 (standard deviation)
Plugging these values into the formula, we can calculate the z-score:
Z = (81 - 75.5) / 4.2
Z = 5.5 / 4.2
Z ≈ 1.31
Therefore, the z-score for a test score of 81 is approximately 1.31.