Standard deviation

Question

The scores on a psychology exam were normally distributed with a mean of 68 and a standard deviation of 6. A failing grade on the exam was anything 2 or more standard deviations below the mean. What was the cutoff for a failing score? Approximately what percentage of the students failed?

Answer 1

               50     56    62    68    74    80    86     

                                     mean

 

Since the standard deviation is 6, you add 6 to the numbers right of the mean

and subtract 6 from the numbers left of the mean.

 

The cutoff would be 56 or anything less than 56.