Statistics 110E -- Statistical and Data Analysis-Psychology/Biological Sciences

Statistic 110 Lab 8

  1. Probability calculations and expectations
  2. Quiz
  3. Discussion of Mini Projects

Probability calculations and expectations

In the Chronicle earlier this week there was an article describing a survey at Duke (and other universities) to investigate cheating and the role of honor codes.

Violation of the honor code is a touchy subject, and it is likely that no one would respond truthfully if asked point blank. While email surveys may be one way to try to get anonymous responses, we will conduct another version of the survey.

Take out a fair coin. Flip it so that it comes up heads or tails, but don't let anyone see the outcome.

When the TA asks, raise your hand if you have 1) a "head" on your coin that you just tossed, or 2) have ever violated the Duke honor code. Since roughly half the class will get heads, it will be impossible to tell who has the coins with heads and who ever violated the honor code, so the responses should be anonymous (just don't let anyone see your coin!)

Using this information, what would you estimate as the number of students that have violated the Duke honor code? Do you think this is accurate?

Chapter 15 Mini Project

For this project, refer to question 12 Chapter 15. Present the question to 10 randomly selected people. Make sure that they are NOT in Stat 110E! Report the proportion who answer with alternative B. Explain to the participants why it cannot be the right answer, and report on their reactions. Turn in a brief (less than 1 page typed) report of your findings.

Chapter 17 Mini Project

For this project, find the sensitivity and specificity of a common diagnostic test with 2 outcomes (positive or negative, disease or not disease). Some examples include genetic tests, drug tests, HIV tests, and pregnancy tests.

A good source for medical information is the Ovid Web pages. Go to the Duke Medical Library and click on Ovid Web Gateway. Then continue by clicking on Generic access -- Start Ovid. Click on Continue to get to the main screen. Select "Best Evidence". This will bring up a search engine; enter the name, i.e. PSA or HIV. You may want to check "Diagnosis" to limit the search to papers about diagnostic procedures.

Note: The test that you report on does not necessarily have to be a medical test, although these often have all the necessary information available.

In your brief (1 page max!) typed report: Describe the test and its purpose. Give the specificity and sensitivity with the correct interpretation so that your grandmother can understand what they mean :-) Calculate the probability of being a "true positive" for someone who tests positive with the test, assuming that the rate in the population is 1 per 100; then calculate the probability assuming that the rate in the population is 1 per 1000. If you can find information on the actual rate in the population, repeat using this information. Turn in the article or abstract where you found the information. Your report should be written so that someone like your grandmother could understand the results.