SOLUTION: on an examination the average grade was 74 and standard deviation was 7 if 10% of the class are given A's and the distribution of grades is to follow a normal distribution then the

Question 1191900: on an examination the average grade was 74 and standard deviation was 7 if 10% of the class are given A's and the distribution of grades is to follow a normal distribution then the lowest possible A and highest possible B if z10=1.28 is?
Answer by math_tutor2020(3817) (Show Source): You can put this solution on YOUR website!

mu = population mean of the class scores = 74
sigma = population standard deviation of the class scores = 7

z10=1.28 indicates the z score for the top 10 percent

This means P(Z > 1.28) = 0.10 approximately

Let's find the raw score x based on this z score
z = (x-mu)/sigma
x-mu = z*sigma
x = mu+z*sigma
x = 74+1.28*7
x = 82.96

The cut off between the highest B and the lowest A is an 82.96
If your teacher is rounding things to the nearest whole number, then it would be an 83.

RELATED QUESTIONS
On an examination the average grade was 74 and the standard deviation was 7. If 12% of... (answered by Theo)

In Statistics and Probability examination, the average grade was 74 and the standard... (answered by ewatrrr)

The mean grade on an examination was 72. and the standard deviation was 9. The top 10%... (answered by Fombitz)

1. A student believes that the average grade on the statistics final examination was 83.... (answered by Boreal)

A set of final examination grades in an introductory statistics course was founded to be... (answered by stanbon)

The senior class has been given a comprehensive examination to asses educational... (answered by stanbon)

An examination was applied to two groups of students, the first with 40 and the second... (answered by Boreal)

A student believes that the average grade on the statistics final examination was 83. A... (answered by Boreal)