WALSH COLLEGE QM 20201Statistical Methods for Business QUIZ

WALSH COLLEGE QM 202-01.Statistical Methods for Business QUIZ #7-FALL 2015 NAME: B NAME: Bntan INSTRUCTOR: G. Cummings The sample size probability when the popula needed to provide a margin of error of 2 or less with a .95 tion standard deviation equals 11 is? (8 points) 1. 2. A random sample of 16 students shows an average age of 25 years and a standard deviation of 2 years. The 98% confidence interval for the true average age of students is? (6 points) 3. In a sample of 500 voters, 400 indicated they favor the incumbent governor. 95% confidence interval of voters not favoring the incumbent is? (6 points) T

Solution

1.

Note that      
      
n = z(alpha/2)^2 s^2 / E^2      
      
where      
      
alpha/2 = (1 - confidence level)/2 =    0.025  
      
Using a table/technology,      
      
z(alpha/2) =    1.959963985  
      
Also,      
      
s = sample standard deviation =    11  
E = margin of error =    2  
      
Thus,      
      
n =    116.2041293  
      
Rounding up,      
      
n =    117   [answer]

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