3 pts You have been given the task of estimating the proport

(3 pts) You have been given the task of estimating the proportion of Southwest flights that arrive “on

time”, (which is no later than 15 minutes after the scheduled arrival time). How many flights must you

survey in order to be 80% confident that your estimate is within .04 of the true population proportion?

Assume that for a recent year, 84% of Southwest flights were on time (based on data from the Bureau

of Transportation Statistics). Show work, answer question, and give units

Solution

Note that      
      
n = z(alpha/2)^2 p (1 - p) / E^2      
      
where      
      
alpha/2 =    0.1  
       
      
Using a table/technology,      
      
z(alpha/2) =    1.281551566  
      
Also,      
      
E =    0.04  
p =    0.84  
      
Thus,      
      
n =    137.9594509  
      
Rounding up,      
      
n =    138 FLIGHTS [ANSWER]