Question 360435
*The first national bank of Wilson has 650 (population) checking account customers. A recent sample of 50 (sample) of these customers showed 26 to have a visa card with the bank. Construct the 99 percent confidence interval for the proportion of checking account customers who have a visa card with the bank.*

The confidence interval for a proportion, {{{pi}}}, is
p ± z σp, where p = 26/50 = 0.52, σp = {{{sqrt(((0.52*0.48)/50))=0.070654}}}(Note that this is just an estimate of the standard error of the proportion, since{{{pi}}} isn't given in the problem), and z = 2.575.  
Thus 0.52± (2.575)*(0.070654), or (0.338066, 0.701934)