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Faced w/ rising fax costs af firm issued a 10 pages or more should be sent via mail, They want the avg. to be 10 or less. Out of 35 fax transmission yielding a sample mean of 14.44 with standard deviation of 4.45 page. At .01 level what is the true mean greater than 10? What is the right tail p-value?

Submitted: 251 days and 9 hours ago.
Category: Math
Value: $9
Status: CLOSED

Accepted Answer

Hi there!

H0 = mean not greater than 10
Ha = mean greater than 10

Use the formula for the z test statistic:
z = (x-mu)/(sd/sqrt(N))
z = (14.44-10)/(4.45/sqrt(35))
z = 5.9028

The critical z value, from a table, for this one tailed test is:
2.3263

Since our test statistic is much higher than the critical value, we REJECT the null hypothesis and believe that the true mean IS greater than 10.

Using Excel...
The formula is: =1-NORMSDIST(5.9028)
The p value is 1.78692E-09
That is WAY below our 0.01 level, so again, we reject the null hypothesis and believe that the mean is greater than 10.


Let me know if you have any questions. If not, thanks for pressing "Accept".

-Scott

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Expert: Scott
Pos. Feedback: 100.0 %
Accepts: 
Answered: 3/16/2009

MIT Graduate

College degree in math... proficient in all levels -- from algebra to calculus

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