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Research on breast feeding and AIDS progression acceleration

8. News flash from Science News (June 2, 2001). Researchers reported that breast feeding children seemed to accelerate the progression of AIDS. A study done in 1993(?!) randomly assigned HIV positive volunteer women to either a breast-feeding or bottle feeding group. Of the 200 women who used commercial formula, 6 died during the 2 year follow-up period. Of the 197 randomly assigned to breast-feeding, 18 women died during the follow-up. Construct the table and use tabi to answer the following questions (6 points).

What was the death rate (% fatality) in the breast-feeding group:_____________
What was the death rate in the formula group:________________
What is the percent difference in mortality between the two groups:_____________
What is the chi-square value of the discrepancy between the actual table and the table of no association:________________________
What is Q:_____________________________
Is AIDS death and infant feeding method related?
9. Now consider the following article, slightly modified to make it easier to analyze, and answer the questions A, B, C, and D below (3 points).
Instant Results From New Test for Lyme Disease
Sep 9 4:00pm ET CHICAGO (Reuters) - A quick, newly approved blood test for Lyme disease eliminates the anxious wait for those who fear they are infected with the tick-borne illness, the researcher who helped develop the test said Sunday. The test, which is as convenient as a pregnancy test, comes in a cassette that requires just a drop of the patient's blood and a half-hour wait at a doctor's office or hospital. Existing tests for the disease require doctors to send the blood sample off to a laboratory and usually do not produce results for a week. Dattwyler's report on the test was published in the journal Archives of Internal Medicine. The studies on hundreds of subjects conducted in 1999 were funded by government grants. Lyme disease is passed on by bites from certain species of ticks carrying the corkscrew-shaped Borrelia burgdorferi bacteria. The number of reported U.S. cases have grown to around 20,000, mostly concentrated in the Northeast, upper Midwest and coastal northern California, though cases have turned up elsewhere. The disease, which can be defeated with a course of antibiotics, initially produces a round rash and flu-like symptoms. Antibiotics are usually administered as soon as there is a suspicion of Lyme disease because when untreated, it can lead to serious complications such as arthritis and problems with the heart, skin, and nervous system. The diagnostic test, which recognizes the patient's own antibodies to the disease through genetic markers, received federal regulatory approval last month and is being marketed to doctors under the brand name PreVue by pharmaceutical maker Carter-Wallace Inc. . In trials with 120 patients with Lyme disease, evenly divided into early, middle, and late stages, PreVue accurately identified Lyme disease in 53 percent of early cases contracted within the previous week, two-thirds of mid-stage cases where the disease had spread to other symptoms, and all of late-stage cases. Unlike the old test, PreVue did not give false-positive results for those with other illnesses such as syphilis and other tick-borne infections, Dattwyler said.
A. What is the sensitivity of the test at each stage of the disease?

B. Now construct the 3*2 table of the results. How many of the 120 participants are identified as having Lyme disease?

C. How many of the 120 participants are false negatives (type 2 errors)?

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