Unformatted text preview: doing a one tail or two tail test and your degrees of freedom to figure out the critical value for t. So if for instance you are doing a one tail test, and your alpha level is .05, and you have df of 150. You look at Appendix C Distribution of t, across the top line for one tail tests, to 0.05, and go down to the infinity row because 150 is > 120df and you find a critical t value of 1.645. Let’s say you calculated t to be 2.6. 2.6 > than 1.645 so you can reject the null hypothesis at alpha level 0.05 for a one tail test. You can even take it further and say that we can reject it at a 0.005 alpha level for a one tail test because 2.6 > than 2.576, the critical value of t at that level. Rejecting the null hypothesis means that there is indeed a difference between the two means and since we are doing a one tail test you can say one mean is greater or less than the other....
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 Spring '11
 Heberle
 Standard Deviation, tail test

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