In: Statistics and Probability
Of 540 Packers fans surveyed, 215 fans were satisfied with the team's draft picks since 2010. Let p represent the proportion of fans that are satisfied with the Packers draft picks.
Create a 99% confidence interval for satisfied Packer fans and give its lower bound as your answer.
Nationwide, football fans since 2010 on average have been satisfied with their team's draft performance 45% of the time. Matt LaFleur wants to know if Packers fans really are less satisfied than the league average. Using the 540 Packers fans sampled in the previous question, LaFleur tests the hypothesis H0 : p = 0.45, Ha : p < 0.45.
Level of Significance,   α =   
0.01          
Number of Items of Interest,   x =  
215          
Sample Size,   n =    540  
       
          
       
Sample Proportion ,    p̂ = x/n =   
0.398          
z -value =   Zα/2 =    2.576   [excel
formula =NORMSINV(α/2)]      
          
       
Standard Error ,    SE = √[p̂(1-p̂)/n] =   
0.0211          
margin of error , E = Z*SE =    2.576  
*   0.0211   =   0.0543
          
       
99%   Confidence Interval is  
           
Interval Lower Limit = p̂ - E =   
0.398   -   0.0543   =  
0.3439
...................
Ho :   p =    0.45  
           
   
H1 :   p <   0.45  
    (Left tail test)      
   
          
           
   
Level of Significance,   α =   
0.01          
       
Number of Items of Interest,   x =  
215          
       
Sample Size,   n =    540  
           
   
          
           
   
Sample Proportion ,    p̂ = x/n =   
0.3981          
       
          
           
   
Standard Error ,    SE = √( p(1-p)/n ) =   
0.0214          
       
Z Test Statistic = ( p̂-p)/SE = (   0.3981  
-   0.45   ) /   0.0214  
=   -2.4220
          
           
         
          
           
   
p-Value   =   0.0077 [excel function
=NORMSDIST(z)]          
   
Decision:   p-value<α , reject null hypothesis
          
           
There is enough evidence to say that Packers fans really are less
satisfied than the league average
...................
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