Question 407275
1. Consider a population with µ = 99.4 and ð = 5.55 (Points : 6) 
(A) Calculate the z-score for x– = 97.3 from a sample of size 38.
z(97.3) = (97.3-99.4)/[5.55/sqrt(38)] = -2.3325
---------------------------------------------------------

(B) Could this z-score be used in calculating probabilities using Table 3 in Appendix B of the text? Why or why not?
If that Appendix is a z-chart the answer is yes.
If it is a t-chart that could also be used.
--------------------------------------------------- 
4. Assume that the population of heights of female college students is approximately normally distributed with mean  of 64.64 inches and standard deviation  of 6.02 inches. A random sample of 98 heights is obtained. Show all work. 
(A) Find the mean and standard error of the x distribution
Your problem statement gives the mean and std.
Maybe you are looking for the mean and std of the 
distribution of sample means which would be
mean of x-bars = 64.64 and std of the x-bars = 6.02/sqrt(98)
=========================================================== 
(B) Find P(x > 63.75)
z or t of 63.75 = (63.75-64.64)/6.02 = -0.1478
=================== 

6. A researcher is interested in estimating the noise levels in decibels at area urban hospitals. She wants to be 98% confident that her estimate is correct. If the standard deviation is 5.09, how large a sample is needed to get the desired information to be accurate within 0.57 decibels? Show all work. 
---
n = [z*s/E]^2*pq
n = [2.3263*5.09/0.57]^2*(1/2)(1/2)
n = 431.55*(1/4)
n = 107.88
Rounding up you get n = 108
================================
Cheers,
Stan H. 
===============