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3 questions, please help me!

karmanbb0802

New member
Joined
Apr 18, 2012
Messages
2
1.
a professor has found that the grades on the statistical final are normally distributed with a mean of 72 and a standard deviation of 12.5the top 8% of the class will receive an A;the next 20%,a B; the next 42%,a C; THE NEXT 18%,a D;and the bottom 12% an F.what average must you obtain to pass the coures?(you'll need a D or better.)


2.
using the central limit theorem.Asuume that women's heights are normally distributed with a mean of 63.6 in.and a standard deviation of 2.5in.
a)if 1 woman is randomly selected,find the probability that herheight is between 63.5 in and 64.5in.
b)if 9 women are randomly selected, find the probability that they have a mean height between 63.5 in and 64.5 in.

3.
using normal distribution as an approximation to the binomial distribution.
66% of all undergraduates received some type of financial aid.suppose 50 undergraduates are selected at random.
a)find the probability that at least 35 received financial aid.
b)find the probability that at most 25 received financial aid.
 

tkhunny

Moderator
Staff member
Joined
Apr 12, 2005
Messages
9,708
1) p(Z > 0.12)?

Seriously, calculate the z-scores and go from there. Let's see what you get.
 

tkhunny

Moderator
Staff member
Joined
Apr 12, 2005
Messages
9,708
Okay, you found the right table. Now how do you intend to use it?

How many standard deviations below the mean will cut off the lowest 12% of the distribution?
 
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