Hi, ME =

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       

85  1.6630  1.9883  2.3710  2.6349   

ME == 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

 

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