# Need Homework Help

#### eyelash

##### New Member
Hello
I am taking a graduate online Statistics course and am having a difficult time with the material. Can anyone offer some guidance in completing the following questions? Your help would be greatly appreciated.

Question #1
Type O A B AB
Rh+ 39 35 8 4
Rh- 6 5 2 1

Use the data in the table, which summarizes blood groups and Rh types for 100 typical people. These values may vary in different regions according to the ethnicity of the population.

Blood groups and Types –If one person is randomly selected, find P (group B or type Rh+).

Question #2
Using the Central Limit Theorem, assume that women’s heights are normally distributed with a mean given by =63.6in and a standard deviation given by =2.5 in.

a. If 1 woman is randomly selected, find the probability that her height is greater than 63 inches.

b. If 100 women are randomly selected, find the probability that they have a mean height greater than 63 inches.

#### JohnM

##### TS Contributor
#1
use the probability rule P(A or B) = P(A) + P(B) - P(A and B)

P (group B or type Rh+) =
[(# in group B) + (# in type Rh+) - (# in both)] / (total #)
= [10 + 86 - 8] / 100

#2
(a) use the normal distribution tables and z-scores --> z = (x-mu)/s
z = (63 - 63.6)/2.5
find the proportion of the area under the curve above z

(b) use the same method and formula, except substitute s/sqrt(n) for s
z = (63 - 63.6)/(2.5/sqrt(100)
find the proportion of the area under the curve above z

If you look in our Examples section, you'll see a post "The Vaunted Normal Distribution."

#### eyelash

##### New Member
Homework Help

John,

Thanks for your reply. It really helped to see it worked out step by step.