Question

a school district requires all graduating seniors to take a mathematics test. This year, the rest scores were approximately normally distributed for the 1208 graduating seniors. This mean score on the test was a 74 and the standard deviation was 11. what percent of the graduating seniors had a test above 85? Express your answers to the nearest percent.

Answer 1

A score of 85 would be 1 standard deviation from the mean, 74.  Using the 68-95-99.7 rule, we know that 68% of normally distributed data falls within 1 standard deviation of the mean.  This means that 100%-68% = 32% of the data is either higher or lower.  32/2 = 16% of the data will be higher than 1 standard deviation from the mean and 16% of the data will be lower than 1 standard deviation from the mean.  This means that 16% of the graduating seniors should have a score above 85%.