Question 1173026
  <pre><font face = "Tohoma" size = 3 color = "indigo"><b> 
Hi, ME ={{{ z*sigma/sqrt(n)}}}
c=.98, X= 15.1 , o=9.0 ​, and n= 85
From table: DF = 85-1 = 84,  , z = 2.3716
DF    0.1     0.05    0.02    0.01 
83  1.6634  1.9889  2.3721  2.6364   
84  1.6632  1.9886  {{{highlight_green(2.3716)}}}     
85  1.6630  1.9883  2.3710  2.6349   
ME ={{{ 2.3716(9)/sqrt(85)}}}= 2.31
CI: 15.1-2.31 < u < 15.1+2.31
CI: 12.79 < u < 17.41
Note:  we used the smaller sample size z = 2.37
NEED to Know:  
What is considered a Large Enough Sample Size  to use z scores below 
	a	a/2	2-tailed crtical regions	
80%	0.2	10%z <-1.28155	z >+1.28155
90%	0.1	5%	z <-1.645	z >+1.645
92%	0.08	4%	z <-1.751	z >+1.751
95%	0.05	2.50%	z <-1.96	z >+1.96
98%	0.02	1%	z <-2.326	z >+2.326
99%	0.01	0.50%	z<-2.576	z >+2.576