Use the normal distribution of SAT critical reading scores for which the mean is

Question

Use the normal distribution of SAT critical reading scores for which the mean is 504 and the standard deviation is 120. Assume the variable x is normally distributed. left parenthesis a right parenthesis(a) What percent of the SAT verbal scores are less than 650? left parenthesis b right parenthesis(b) If 1000 SAT verbal scores are randomly selected, about how many would you expect to be greater than 550?

left parenthesis a right parenthesis(a)

Approximately _ % of the SAT verbal scores are less than 650.

Explanation / Answer

Sol:

(A):

P(X<650)

z=x-mean/sd

=650-504/120

=1.217

P(Z<1.217)

use the standard normal table to find this area.

From Standard Normal Table

Step 3: We conclude that:

P ( Z<1.217 )=0.8888

Solutionb:

P(X>550)

z=550-504/120

z=0.383

P ( Z>0.383 )=1P ( Z<0.383 )=10.648=0.352

sample size*prob=1000*0.352=352

352 scores expect to be greater than 550

Related Questions

Navigate

• Browse (All)
• Browse U
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.