Posted by troy on Tuesday, February 21, 2012 at 10:04am.
To determine whether or not to use a two-tailed test versus a one-tailed test depends on the alternate hypothesis. If the alternate hypothesis shows direction (less than or greater than), a one-tailed test is used. If the alternate hypothesis shows no specific direction, then a two-tailed test is used. Usually a problem will give you a clue as to whether to use a one-tailed or two-tailed test. For example, the problem might ask only if there is a difference (two-tailed), or a problem might look for less than a population value or greater than a population value (one-tailed).
You can reduce Type I errors (rejecting the null when it's true) by setting the alpha at a lower level; however, when you do that, you increase the probability of making a Type II error (accepting the null and it's false). Most researchers try to minimize errors by setting alpha to .05.
I hope these few explanations will help.
Related Questions
statistics for behavioral sciences - In a one- to two-page Microsoft Word ...
Applied Statistics - Assignment Guidelines Perform a two-tailed hypothesis test ...
statistics - Perform a two-tailed hypothesis test on the intrinsic variable AND ...
writing - "Part 1: Write an exploratory essay in which you compare and ...
Keyboarding and Wording processing? - 18. To start keying a new page of a ...
Natural Sciences - Which one of the disciplines listed here includes essays and ...
Natural Sciences - Which one of the disciplines listed here includes case ...
computer - I need to do the degrees celcuis and fahrenheit abreviations on my ...
Natural Sciences - Which one of the disciplines listed here includes journal ...
Natural Sciences - Which one of the disciplines listed here includes direct ...
For Further Reading