In a study of the length of time that students require to ea

In a study of the length of time that students require to earn bachelor’s degrees, 60 students are randomly selected and they are found to have a sample mean of 4.8 years and a sample standard deviation of 2.2 years, construct a 95% confidence interval estimate of the population mean.

Solution

Note that              
Margin of Error E = z(alpha/2) * s / sqrt(n)              
Lower Bound = X - z(alpha/2) * s / sqrt(n)              
Upper Bound = X + z(alpha/2) * s / sqrt(n)              
              
where              
alpha/2 = (1 - confidence level)/2 =    0.025          
X = sample mean =    4.8          
z(alpha/2) = critical z for the confidence interval =    1.959963985          
s = sample standard deviation =    2.2          
n = sample size =    60          
              
Thus,              
Margin of Error E =    0.556666577          
Lower bound =    4.243333423          
Upper bound =    5.356666577          
              
Thus, the confidence interval is              
              
(   4.243333423   ,   5.356666577   ) [ANSWER]