:5aa. Solution.  20% of the tickets in the sample are marked
with a 4, which will be the center of the confidence interval. 
To find the SE of the percentage of 4's in a sample of size 100,
we begin by creating a new population by replacing every 4 with a
1 and every 4 with a 0.  This gives us a 0-1 population and a 0-1
sample.  Estimating the (new) 0-1 box by the (new) sample
average, we get

 	
 box SD = square root of .2 x .8 = (.16)^(1/2) = .4 

 	
 SE for the sum = .4 x square root of 100 = .4 x 10 
 	
  = 4 

 	
 SE for % = 4/100 x 100% = 4%, 


so an approximate 99.7% confidence interval is given by
 20 +/  (3x4%) = 20 +/  12%. 	& &I