Hi,

Can anyone explain me please how to do this problem?

1. A teacher informs her organic chemistry class (of 500+ students) that a test was very difficult, but the grades would be curved. Scores on the test were normally distributed with a mean of 44 and a standard deviation of 8.9. The maximum possible score on the test was 100 points. Because of partial credit, scores were recorded with 1 decimal point accuracy. (Thus, a student could earn a 44.3, but not a 43.17.)

The grades are curved according to the following scheme. How ca I find the numerical limits for each letter grade .

Letter Scheme Interval

A Top 11%

B Scores above the bottom 70%and below the top 11%

C Scores above the bottom 30%and below the top 30%

D Scores above the bottom 11%and below the top 70%

F Bottom 11%

2.NOTE: This problem has many steps. I am asked to enter intermediate values in the process. These answers will require a fixed number of decimal points. However, REMEMBER that you are not using the rounded numbers in your future calculations. The only exception to this is that you may usez-scores rounded to three decimal places (of course, you also may use the unrounded version as well).

In a certain school district in a large metropolitan area, the SAT scores over that past five years are normally distributed with a mean of 1529. Furthermore,P30is 1382.

For a normal distribution, what is thez-score for the 30-th percentile?

z=

(Enter answer rounded to three decimal places.)

Using this information, what is the standard deviation of this population of SAT scores?

sigma =

(Enter answer rounded to the nearest whole number.)

For a normal distribution, what is thez-score for the 95-th percentile?

z=

(Enter answer rounded to three decimal places.)

Now, use all of the information to determine what theP95

score is for this population?

P95=

I do not understand how to calculate the P.

Thank you for your help!!