Question 481140
  <pre><font face = "Tohoma" size = 4 color = "indigo"><b> 
Hi,
95% confident of estimating the population mean to within a sampling error of ± 2
ME = 1.96{{{alpha/sqrt(n)}}}
2 = 1.96{{{13/sqrt(n)}}}
{{{sqrt(n) = 1.96*13/2}}}
     n = (1.96*13/2)^2
     n = 162.3076, 163 rounded up

	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