<PRE><B>Question 136316</B>
A Cell phone company offers two plans to its subscribers. At the time new subscribers sign up they are asked to provide some demographic information. 
The mean yearly income for a sample of 42 subscribers to plan A is $57,000 with a standard Deviation of $6,000. 
For a sample of 50 subscribers to plan B the mean income is $63,000 with a standard deviation of $4,900. 
At a significance of 0.05 is there a difference in between the two plans? 
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Comment: I don&#39;t think you are comparing plans; you are comparing income
of plan purchasers.
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Ho: u(A)=u(B) 
H1: u(A) is not equal to u(B)
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Alpha:5%
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CV:+-1.96
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What Formula?
Test statistic for 2-Sample T-test: 
t(57000-63000) = (-6000)/sqrt[(6000^2/42)+(4900^2/50)]=-5.188..
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Conclusion: since test stat is in the rejection interval, Reject Ho.
Income of plan A and plan B purchasers are not the same.
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Cheers,
Stan H.

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