SOLUTION: The average attrition rate of a customer based company is 20% with a standard deviation of 7% (based on the past data). To test this a sample of 100 was taken and 23% average attri

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Question 1030980: The average attrition rate of a customer based company is 20% with a standard deviation of 7% (based on the past data). To test this a sample of 100 was taken and 23% average attrition rate was found. What can be concluded from about the attrition rate at 10% significance level?
The attrition rate is 23% now
The attrition rate is more than 20% now
The attrition rate is same as 20%
The attrition rate is less than 20% now
I tried this and got the below answer.Can you please check if this is correct.
H0-No diff in attrition rate
H1:Increase in attrinium rate
x>=23=1-(x<=23)
==1-NORM.DIST(23,20,7/(100)^0.5,TRUE)
=9.10765E-06 <0.1
reject null hypothesis
Is option (a) the correct answer that the attrition rate is 23% now.
Thanks

Answer by ewatrrr(24785)   (Show Source): You can put this solution on YOUR website!

Hi,
re: Your reply (Idea being..with a 7% SD ... the 3% difference in the test sample
would be expected to be consistent with the average of 20%)
I. Yes, .07/sqrt(100)
II. With Excel function: P(z <4.29)) = NORMDIST(4.29) = .999
Ho: p = 0.2
Ha: p > 0.2 (claim)
sample proportion = .23
z(.23) = (.23-.2)/.07/sqrt(100) = .03/.007 = 4.29
p-value = P(z < 4.29) = .999 OR 99.9% (10% significance level)
p-value greater than 10%, accept Ho
The attrition rate is same as 20%

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