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Question 569:



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  1. Q569_1_MegaStatExcelInstructionsQ569.xls

We can use a 1-sample t test.

  1. The null hypothesis is that the mean number of faxes pages is less than or equal to 10 : Ho: μ 10
  2. The alternative hypothesis is the mean number is greater than 10. Ha: μ > 10


Our test statistics will be the t-statistic. To get this value we first subtract the observed mean from the test mean 14.44-10 = 4.44 and this becomes the numerator for our test statistic.

  1. Find the standard error of the sample mean (SEM) which is the standard deviation divided by the square root of the sample size 4.45/SQRT(35) =.75219. This is the denominator for the test statistic.
  2. Dividing the fraction we get 4.45/.75219 = 5.9028, which is our test t-statistic.
  3. Now we need to find the 1-sided probability associated with this statistic. To find that we can use the excel function =TDIST(5.9028,34,1) and we get the p-value less than .00001. Where the parameters in the excel function are the test statistic, the degrees of freedom (35-1) and 1 tail probability. We can also use the calculator available here http://www.usablestats.com/calcs/1samplet&summary=1 and enter the data and we get the same result p <.00001.

With a p-value lower than .01, we reject the null hypothesis and say there is sufficient evidence that the mean number of fax pages is greater than 10.

See the attached file for MegaStat instructions, output and the TDIST formula example.

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