| Stat 251:Statistical Methods I |
Fall 2008 |
Goal: To collect, describe, and analyze using the methods of Chapter 1 (i.e. Fisher's Exact Test).
The Study: You should think of two groups that you can compare with one binary categorical variable through an experiment or an observational study. You are free to choose your own topic. The question may be related to your major or some other topic of interest. Make sure you choose a topic for which it is feasible to gather the data in a relative short period of time, or for which you have access to data from another class or professor. For example, you could observe men and women on campus to determine whether they are left or right handed, or you could randomly assign people to take a survey with two different wordings and see if they respond differently depending on how the question is asked. Your study must obtain at least 15 observational/experimental units in each explanatory variable group.
Teams: You may work in teams of 2 people if you wish. It is up to the members of the group to make sure everyone contributes equally. Plan your schedules so that you will have time to work together on the project outside of class. Teams should be formed and project topics selected by Friday, September 26th. You may be asked to share your proposals with the rest of the class. You must have your ideas approved by me before you begin collecting any data. Please start early so you have time to ask questions.
Final Report: Due Friday, October 10th. This should be a typed report, written collaboratively by all team members. Your report should be written as to other student researchers. Make sure it includes at least:
I. Introduction – Why did you choose this topic? What did you expect to find? Have similar studies been done elsewhere? Why should the reader be interested in your results and continue reading?
II. Summary of Data Collection Methods – How did you collect the data? What were the observational units? What groups did you compare, how did you find them/form them? Was this a prospective or retrospective study? Observational or Experiment? What was your response variable? How were these variables measured? What additional “controls” did you exert on the study? (E.g., did you only observe people writing or did you take any behavior such as throwing a football as indication of handedness?) Did you have any “operational definitions”? (E.g., did you pre-test any of the questions on a test group to see if the wording was clear?) Any non-response or other unexpected results? Did anything go wrong during the course of the study? (Note: You can never give me too much detail in this section!) In particular, there should be enough information that someone else could replicate your study on their own based only on your description (and hopefully improve upon it based on your suggestions below).
III. Analysis of Results – Include appropriate numerical and graphical summaries of your data, including the two-way table. Write several paragraphs explaining what you found in these data. Use both simulation (using the Java applet) and Fisher’s Exact Test (using Minitab) to analyze your results, reporting both the approximate and exact p-value (and include the output – you can make a screen capture of the applet window using the Print Screen key on the keyboard). Include a careful interpretation of what this p-value tells you. Is the difference statistically significant? What conclusions can you draw? Be sure to refer back to the type of study conducted in explaining the scope of your conclusions. Address both the question of causation and the question of whether you believe your findings generalize to a larger population. (Note: All computer output should be included in the body of the report. Make sure all figures and graphs are clearly labeled.)
IV. Conclusion – Summarize the results of your study. What did you learn? Did the data behave as you expected? Critique the methods used to collect the data. Is there anything you would do differently next time? How might this affect the conclusions of the study? What similar questions might someone chose to investigate in the future to build on your results?