ProfessorBrehmhas decided to give a standardized statistics exam that is nationally normed, meaning that we can use the normal model and the population mean and standard deviation are known values. The normal model is N(80, 6) which tells us the mean statistics score is 80 with a standard deviation of 6.

ProfessorBrehmcurrently uses a 10-point scale (100-90 A, 80-89 B, 70-79 C, 60-69 D, below 60 F) but wants to scale her own students' tests based on this data by using the percentiles. She needs to find the new values that correspond to the 90th, 80th, 70th and 60th percentiles, which will give the new lower value for each grade scale. Simple right?

For your first post, find the values that correspond to the 90th, 80th, 70th and 60th percentiles, either with or without z-scores. Then give the new range. Remember that your range should have an upper and lower value. As always, post a picture of Excel output,and include anyexplanation needed.Yes, this is a difficult question. As always, remember I don't expect perfection on the first post. Give it a go, then make corrections as necessary.

For your second post, either provide quality feedback to a classmate or devise a new grading scale based on standard deviations. Award an A for students 2 or more standard deviations above the mean of the standardized test, a B for students from one up to 2 standard deviations above the mean, C for students from one standard deviation below the mean to one standard deviation above the mean, D for students with scores from two standard deviations below the mean to one standard deviation below and an F for students who score more than two standard deviations below the mean of the standardized test. Provide the new scale along with any relevant work.