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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