A set of 80 sociology tests with a normal distribution has a mean score of 65 and a standard deviation of 8. Shellie scored in the 90th percentile of the class. What score did she receive? A) 0.52 = (X_i + 65)/8 = 60.84 B) 1.28 = (65 - X_i)/80 = 63.44 C) 1.28 = (X_i - 65)/8 = 75.24 D) 100 = (X_i + 10)/1 = 90

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Quizplus · Accepted Answer

The 90th percentile corresponds to a z-score of approximately 1.28. Using the formula X = μ + zσ, where μ is the mean and σ is the standard deviation, Shellie's score is 65 + 1.28(8) = 75.24.

A Set of 80 Sociology Tests with a Normal Distribution