Question

if you're constructing a 95% confidence interval for the MEAN of some population, and you collect a sample of size 100 that has a sample mean of x-bar=30 with a population standard deviation of _=20, then how much would the margin of error of the confidence interval be? use 3 decimal places of accuracy

Answer 1

    Given          
   X̅ = 30 ...sample mean
   n = 100   ...sample size       
   σ = 20   …population standard deviation      
              
   For 95% confidence interval, Z-value is obtained using the Excel function NORM.S.INV          
   α = 0.05           α/2 = 0.025          
   z = NORM.S.INV(0.025)          
   z = 1.96   …We use the positive value of z      
              
   Margin of Error(ME) is given by          

             = 3.920

   

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