Question

If class grades have a mean of 72 and a standard deviation of 5, what is the probability of grading higher than 72?

a) 0.5
b) 0.8413
c) 0.1587
d) 0.8413

Answer 1

To find the probability of grading higher than 72, we can use the z-score formula and the z-table.

Step-by-step explanation:

To find the probability of grading higher than 72, we need to find the area under the normal distribution curve to the right of 72. Since the mean is 72 and the standard deviation is 5, we can use the z-score formula to calculate the z-score for 72. The z-score formula is z = (x - μ) / σ, where x is the given value, μ is the mean, and σ is the standard deviation.

For 72, the z-score is (72 - 72) / 5 = 0. According to the z-table, the probability to the right of the z-score of 0 is 0.5. Therefore, the probability of grading higher than 72 is 0.5.