The grades on the last history test had a mean of 80%. Assume the population of grades on history exams is known to be distributed normally, with a standard deviation of 5%. Approximately what % of students earn a scoore between 70% and 80%.

Question

The grades on the last history test had a mean of 80%.  Assume the population of grades on history exams is known to be distributed normally, with a standard deviation of 5%.  Approximately what % of students earn a scoore between 70% and 80%.

krisssssssssssss · Answer

80 - 70 = 10. The standard deviation is 5. Therefore the grade of 70% is 2 standard deviations below the mean. The empirical rule states that for all normal distributions approximately 95% of the data points lie within the range of plus and minus 2 standard deviations of the mean. In this case only half of the data points in this range are needed, so the required percentage is. :)

sueann · Answer

It is what percentage?

krisssssssssssss · Answer

sorry my sentence cut off it was *95%

sueann · Answer

Thanks