Answer:
a) 
With:


b) 

c) 

d) 


Step-by-step explanation:
For this case we know the following propoertis for the random variable X

We select a sample size of n = 81
Part a
Since the sample size is large enough we can use the central limit distribution and the distribution for the sampel mean on this case would be:

With:


Part b
We want this probability:

We can use the z score formula given by:

And if we find the z score for 89 we got:


Part c

We can use the z score formula given by:

And if we find the z score for 75.65 we got:


Part d
We want this probability:

We find the z scores:



Answer:
0.5
Step-by-step explanation:
we see that A is 1 of 2 choices, so theoretically, P(A) = 1/2 = 0.5
Answer:
3/11
Step-by-step explanation:
Divide both the numerator and denominator by 2.

Answer:
y>4x-4
Step-by-step explanation:
Answer:
Option c -2.8571
Step-by-step explanation:
z-score are calculated as
.
We are given that mean=120 and standard deviation=S.D=35 as X~N(120,35).
Sample size=n=25.
We have to find z-score for x-bar=100. So,
z-score=[100-120]/[35/√25]
z-score=[-20]/[35/5]
z-score=-20/7
z-score=-2.8571.
Thus, the z-score associated with x-bar = 100 is -2.8571.