Ohio Assessments for Educators (OAE) Mathematics Practice Exam

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How is the Z-score calculated?

(x + mean)/SD
(mean - x)/SD
(x - mean)/SD
(x * mean)/SD

The correct answer is: (x - mean)/SD

The Z-score is a statistical measurement that describes how many standard deviations a data point (x) is from the mean of a data set. To calculate the Z-score, you subtract the mean from the data point and then divide that result by the standard deviation (SD). This formula allows you to standardize scores on different scales and make comparisons across different distributions. In this case, the correct formula for calculating the Z-score is (x - mean)/SD. Here, "x" represents the data point you are evaluating, "mean" is the average of the data set, and "SD" is the standard deviation. If you have a Z-score of 0, it indicates that the data point is exactly at the mean. A positive Z-score indicates that the data point is above the mean, while a negative Z-score indicates it is below. The other formulas do not accurately represent the calculation of a Z-score. The formulas involving addition, subtraction, or multiplication inappropriately manipulate the values instead of placing them in the context of standard deviation from the mean.