Question 610782
  <pre><font face = "Tohoma" size = 3 color = "indigo"><b> 
Hi, 
50 calls initiated on cellular car phones with mean duration of 3.5 minutes & SD = 1.2 minutes
Find 99% confidence interval for the mean duration of telephone calls initiated on a cellular car phone.
  ME = {{{ 2.576*1.2/sqrt(50)}}} = .437
 CI: 3.5-.437> u < 3.5+.437
 CI: 3.063 > u < 3.947
Note: -------------------------------------------------------------
	a	a/2	crtical regions	
80%	0.2	10%	z <-1.28155	z >+1.28155
90%	0.1	5%	z <-1.645	          z >+1.645
92%	0.8	4%	z <-1.751	          z >+1.751
95%	0.05	2.50%	z <-1.96	          z >+1.96
98%	0.02	1%	z <-2.33	          z >+2.33
99%	0.01	0.50%	z<-2.576	          z >+2.576