DO I NEED TO USE 2-TAILED OR 2-TAILED RESULTS? WHY?
A researcher believed that 2 hours per week of intensive exercise would result in significant weight loss after 12 weeks on the schedule. Accordingly, he weighed a group of 50 subjects before and after the 12 week exercise period.
I would use a one tailed result. http://en.wikipedia.org/wiki/One-_and_two-tailed_tests
Rawr
To determine whether you should use a one-tailed or two-tailed test in this situation, you need to consider the specific research question and hypothesis you are testing.
In a one-tailed test, you are only interested in seeing if there is a significant effect in one direction. For example, in this case, the researcher might expect that the 2 hours of intensive exercise would result in weight loss. So, the one-tailed hypothesis would be: "2 hours per week of intensive exercise will result in significant weight loss after 12 weeks."
On the other hand, a two-tailed test is used when you are interested in detecting any significant effect, regardless of the direction. In this case, if the researcher is open to the possibility of weight gain or weight loss, the two-tailed hypothesis would be: "2 hours per week of intensive exercise will result in a significant change in weight after 12 weeks."
To decide which type of test to use, you should consult with the researcher or refer to the study's objectives and hypothesis. It is important to choose the appropriate test to ensure the statistical analysis accurately corresponds with the research question being investigated.