[SOLVED] HP010335701.aspx

tTest in Excel

Preparing Data
Assume we are considering whether a new marketing campaign has increased sales in a group of six sales territories. In this example, the sample size (n) equals 6, then degrees of freedom = n 1 = 5.

Copyright By Assignmentchef assignmentchef

The data in Excel:

Operations in Excel
In Excel, t-Test is described as follows (this is Excel 2003):
If [Data > Data Analysis] does not exists then do the following:
v[File > Options > Add-Ins > Analysis ToolPak > Go > (click both Analysis ToolPak and Solver Add-in then OK)]
[Data > Data Analysis > t-Test: Paired Two Sample for Means] This following dialogue box will appear:

Input the data as followings:
Variable 1 Range: Select everything that is highlighted light blue, including the label Sales After. If you are trying to determine whether
the after measurements have gone up, the after data is Input Variable 1. If you are trying to determine whether the after measurements have gone down, the after data is Input Variable 2.
Variable 2 Range: Select everything that is highlighted in yellow, including the label Sales Before.
Hypothesized Mean Difference: 0
Labels: Check the box because you included the labels for Variables 1 and
Alpha: This depends on your desired degree of certainty. 0.05, if you desired 95% certainty. 0.20 if you desire 80% certainty.
Output Range: Select the cell that you want the output to appear in.

Hit OK to run the analysis and the following Excel output will appears:

This output can be interpreted as follows:
The t value is 2.359.
One-tailed Test
Thistvalueisgreaterthanthecriticaltvalueforaone-tailedtest (2.132). We can therefore state with 95% certainty that the mean sales has increased as a result of the new marketing campaign.
TheaboveconclusioncanalsobereachedbecausethepValueforthe one-tailed test (highlighted in light blue on the Excel output) is 0.039. This is less than alpha (0.05). The p Value being less than alpha is an equivalent result to the t value being greater than the t critical value.
ThepValuebeinglessthanalphaalsomeansthenullhypothesiscan be rejected.

Two-Tailed Test
A different result is arrived at for the two-tailed test. The two- tailed test is more stringent because the alpha region of uncertainty (5% of the area under the students t distribution curve) is now divided between both outer tails. The t value needs to be larger for the two-tailed test to wind up in the outer 2.5% area of either outer tail.
In this case, the t value was not large enough to be positioned in the outer 2.5% of either outer tail. The t value (2.359) is smaller than the critical t value for the two-tailed test (2.776). This indicates that it cannot be stated with 95% certainty that there has been a change in the mean from before to after.
The p value calculated for the two-tailed test (0.078) is larger than alpha (0.05). This is an equivalent result to the above.

References
1. http://blog.excelmasterseries.com/2010/08/how-to-use-t-test-in-excel- to-find-out.html
2. http://www.ats.ucla.edu/stat/mult_pkg/faq/general/tail_tests.htm
3. http://en.wikipedia.org/wiki/One-_and_two-tailed_tests
4. http://www.addictivetips.com/windows-tips/excel-2010-data-analysis/
5. http://office.microsoft.com/en-au/excel-help/t-test-function- HP010335701.aspx
6. http://labstats.net/articles/pvalue.html

CS: assignmentchef QQ: 1823890830 Email: [email protected]