Directional and nondirectional hypotheses

 

 

When computing a t-test, it is important to distinguish between directional and nondirectional hypotheses as the direction will determine the rejection regions. Describe how the rejection regions would differ according to the type of hypothesis you would use.

An insurance company asks you to determine whether older drivers are safer than younger ones. Provide a directional hypothesis related to this study. Then, explain how you would need to change the hypothesis so that it would be nondirectional. What happens to the rejection regions and why? Which of the two hypotheses do you think is more appropriate and why?

Justify your answers with appropriate reasoning and research from your textbook and course readings. Start reviewing and responding to at least two of your classmates as early in the week as possible. You can ask technical questions or respond generally to the overall experience. Be honest, clear, and concise. Always use constructive language, even in criticism, to work toward the goal of positive progress. Using questions and seeking clarifications are good ways to make your reviews substantive!

Directional and nondirectional hypotheses

 

Directional and nondirectional hypotheses can be easily interchanged according to the hypothesis the researcher is testing. For instance, a drug company might predict that a drug will help a subject lose weight while another drug company might predict that a drug will alter a subject’s weight.

Describe a situation in which you would test a directional hypothesis. Be sure to state the independent variables (e.g., drug or placebo) and the dependent variables (e.g., weight loss) clearly and explain why the hypothesis is directional. Then, revise the same situation to make it nondirectional. Explain which according to you is more appropriate and why. Evaluate the practice of altering the alpha level so that a two-tailed test will have a 5% rejection region on both sides of the curve for a total of 10% instead of having a 2.5% rejection region on both sides in order to maintain a 5% alpha.

Justify your answers with appropriate reasoning and research