Please help with Z-scores

#1
Please help!!

You are given a 2003 summary report of SAT scores for 1,000 grade 9 students from a large county in Florida. The scores are assumed to be normally distributed, and have a mean of 500 and a standard deviation of 80.

1. For this distribution determine which scores are associated with each of the following z-scores: -2,-1,0,1,2.

2. For this distribution determine the percentage of examinees that fall below each of the z-scores in question 1 (e.e. what is the percentile rank associated with each of the z-scores).

Please give me some direction in how to compute this.
Thank you,
latonya
 
#2
z = (observed - mean)/standard deviation

1. solve above for observed and plug and chug -2,-1,0,1,2.

2. look up z scores in tables, or use the empiracle rule with subtraction and division.

Peter
 
#3
1. For the first part you need to plug in each of the z-scores as well as mean=500 and s.d.=80. For example, for z-score=-2, the equation will be
-2=(x-500)/80. Then you solve for x and that is your answer for which value is associated with a z-score of -2.
2. For second part, just look up the values of the z-scores mentioned in part 1 on the z-table.
 
#4
Z-scores!! Please help!!

Can someone please help me with the second part of this questions. How do I find the percentile rank. Can someone show me how to get the percentile rank for one of the z-scores as an example.

You are given a 2003 summary report of SAT scores for 1,000 grade 9 students from a large county in Florida. The scores are assumed to be normally distributed, and have a mean of 500 and a standard deviation of 80.

1. For this distribution determine which scores are associated with each of the following z-scores: -2,-1,0,1,2.

2. For this distribution determine the percentage of examinees that fall below each of the z-scores in question 1 (e.e. what is the percentile rank associated with each of the z-scores).