Question 662429
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Hi,
Re TY
99% confidence interval
Two-Tailed
z(.01/2)=z(.005)=  2.576
If we wish to have a 99% confidence interval in a Two-Tailed situation
what that is saying is that a 'z' found to fall in the critical regions... 
that is z<-2.576 Or  z >+2.576 falls outside the confidence interval.
Each confidence interval has its own critical regions as shown below.

	a	a/2	critical regions	
80%	0.2	0.100	z <-1.282	        z >+1.282
90%	0.1	0.050	z <-1.645	        z >+1.645
92%	0.8	0.040	z <-1.751	        z >+1.751
95%	0.05	0.025	z <-1.96	        z >+1.96
98%	0.02	0.010	z <-2.326	        z >+2.326
99%	0.01	0.005	z<-2.576	        z >+2.576