The mean score on a particular test is 79 and the standard deviation is 5.5. What is the probability that a randomly selected test score is more than 90?

Question

34%
5%
95%

Answer 1

Based on a z-table or calculator, we can find that a score of 90 is approximately 1.64 standard deviations above the mean.

To find the probability of a score being more than 90, we need to find the area to the right of 1.64 standard deviations on a standard normal distribution curve. This area is approximately 0.0505 or 5%.

Therefore, the probability that a randomly selected test score is more than 90 is 5%.