Question

Confidence Intervals and Minimum Sample Sizes

     Use your set of z-scores to find the following:

1. A survey of 145 randomly selected college students showed that only 87 checked their campus email on a regular basis. Construct a 90% confidence interval for the percentage of students at that college who do check their email account on a regular basis.

Answer 1

We have given,              
              
x=87          
n=145          
Estimate for sample proportion=0.6  
Level of significance is =1-0.90=0.1      
Z critical value(using Z table)=1.645      
              
Confidence interval formula is              


=(0.5331,0.6669)
              
Lower limit for confidence interval=0.5331  
              
Upper limit for confidence interval=0.6669