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IT 121 -- Activity A9

Submit: An Excel file with your answers.
Clearly label Part 1 and Part 2. For a lot of Part 2 answers, you might want to create text boxes to write in.
Work in groups of two or three.

Part 1 - Correlation and Linear Trend

Goal:   Investigate the relationship between smoking while pregnant and the childs birthweight.

  1. Download the Excel file CigarettesBirthweight.xls to your harddrive.

  2. What is the correlation r between number of cigarettes smoked per day and birth weight?

  3. Form the scatterplot of birth weight (y-value) vs. number of cigarettes smoked per day (x-value).

  4. Add a linear trend line to the scatterplot in 3. Also add the R2 and trend line equation to the plot.

  5. Does the relationship between x and y appear to be a linear association?

  6. What is the equation of the linear trend line?

  7. What is the predicted birthweight for a mother that smokes twenty cigarettes per day?

  8. What is the predicted birthweight for a mother that does not smoke at all?

Part 2 - False Positive and Negative Test Results

Goal:   Investigate how false positives and negatives affect the accuracy of medical tests.

  1. The numbers for a particular type of cancer are as follows:

  2. Create a table similar to the one in the May 12 Lecture Notes, which displays the number of true positives, false positives, true negatives and false negatives. Make sure you label everything.

  3. Compute the probability that a patient really has cancer, given a positive blood test.

  4. Compute the probability that a patient has cancer, even with a negative blood test.