Question

A random digit dialing telephone survey of 908 drivers asked, "Recalling the last ten traffic lights you drove through, how many of them were red when you entered the intersections?" Of the 908 respondents, 185 admitted that at least one light had been red.  

Give a 96% confidence interval (±0.001) for the proportion of all drivers who ran one or more of the last ten red lights they met:    ⩽p⩽⩽p⩽ .

Answer 1

We have given,              
              
x=185          
n=908          
Estimate for sample proportion=   0.2037  
Level of significance is =1-0.96=0.04      
Z critical value(using Z table)=2.054      
              
Confidence interval formula is              


=(0.176,0.231)

0.176<p<0.231