Question

Find an 80% confidence interval for the proportion of all college students who have at least one credit card.

In a survey of 1530 undergraduate students, 1187 reported that they had one or more credit cards.

a) (0.7380, 0.7823) (b) (0.7549, 0.7967) (c) (0.7583, 0.7934) (d) (0.7622, 0.7895) (e) (0.7756, 0.7760)

Answer 1

(d) (0.7622, 0.7895)

We have given here,          
          
x=1187      
n=1530      
Estimate for sample proportion=0.7758
Level of significance is =1-0.80=0.2  
Z critical value(using Z table)=1.282  
          
Confidence interval formula is          


=(0.7622,0.7895)