Need major help w/ inverse normal dist. of SAT, ACT scores

[sabbycat]

The first part I got, but i am having problems on the bottom part of A,B, and C, need some help please

Inverse Normal Distribution: SAT and ACT Scores:. What is the probability that a randomly selected high school senior's score on the mathematics part of the SAT will be?

(a) more that 675? P(x > 675) = P(z > 1.75) = 0.0401

(b) less than 450? P(x < 450) = P(z < 0.50) = 0.3085

(c) between 450 and 675? P(450 ? x ? 675) = P(-0.50 ? z ? 1.75) = 0.6514

What is the probability that a randomly selected high school senior's score on the mathematics part of the ACT will be

(d) more than 28? P(x > 28) = P(z > 1.67) = 0.0475

(e) more than 12? P(x > 12) = P(z > -1.00) = 0.8413

(f) between 12 and 28? P(12 ? x ? 28) = P(-1.00 ? z ? 1.67) = 0.7938

When answering the questions below refer to the SAT and Act information from above.

a) Suppose that an engineering school honors program will accept only high school seniors with mathematics SAT or ACT score in the top 10%. What is minimum SAT score in mathematics for this program? What is the minimum ACT scores in mathematic for this program?

b) Suppose that an engineering school will accept only high school seniors with mathematics SAT or ACT score in the top 20%. What is the minimum SAT score in mathematics for this program? What is the minimum ACT score in mathematics for this program?

c) Suppose that an engineering school will accept only high school seniors with mathematics SAT or ACT score in the top 60%. What is the minimum SAT score in mathematics for this program? What is the minimum ACT score in mathematics for this program?

 

[royhaas]

Start with the percentiles of the standard normal distribution. Top 10 percent is the 90th percentile.

 

[sabbycat]

Ugg still not understanding :x

 

[stapel]

Ugg still not understanding :x

If you aren't familiar with the basic percentiles related to standard normal distributions, means, and standard deviations, then you need waaaaaaaay more help than we can here provide. (You're missing at least a chapter from the book!) :shock:

Please seriously consider hiring a qualified local tutor and setting aside an hour or two a day for concentrated re-teaching. By working with you face-to-face, your tutor will be well-placed to figure out how many sections or chapters of material you're missing, and can try to help you get caught up to your class. :idea:

My best wishes to you in your studies!

Eliz.