Question

Page 2 of 8 4. Fill in the blank. Ascribing the characteristics o is called the f a group to every individual in that group 5. Low body weight, substance abuse, or HIV infection can each individually cause a patient to evelop active TB disease without the other two factors, but only when followed by exposure to TB bacterium. Exposure to TB bacterium alone is not followed by active TB disease, but the active TB disease never occurs in the absence of exposure to TB bacterium HIV infection is considered a. A sufficient, but not necessary, cause b. A necessary, but not sufficient, cause c. A necessary and sufficient cause d. Neither necessary nor sufficient e. None of the above 6. A case-control study was done to evaluate the association between voice disorders and being a high school teacher. Cases with voice disorders were matched to controls without voice disorders according to smoking status, age, and gender. Researchers reported a matched-pairs odds ratio of 2.0 for the comparison of high school teachers to non-teachers on voice disorders. The study findings above may not be valid because: a. Exposure may have been protective related to disease b. Smoking likely caused the elevated odds ratio c. Disease rates were compared between cases and controls d. The exposure is extremely difficult to detect and measure e. None of the above 7. In a cohort study, the advantage of starting by selecting a defined population for study before any of its members become exposed, rather than starting by selecting exposed and non-exposed individuals, is that a. The study can be completed more rapidly b. A number of exposures can be studied simultaneously A number of outcomes can be studied simultaneously d. The study will cost less to carry out . a and d c.

Answer 1

5. Ans: a

A sufficient but not necessary cause.

HIV infection is sufficient for the TB bacterium to attack an individual but that alone is not a cause. Persons with HIV are alive without TB infection as they maintain proper nutrition. It just increases the vulnerability to TB infection.

6. Ans: b

Smoking slightly caused the elevated odds ratio.

Exposure to continuous teaching is not protective related to the disease.

Smoking is one of the contributing factor for voice disorders. So it may cause an increase in voice disorders on the side of control group thereby causing slight changes in ratio.

7. Ans: d

The study will cause less to carry out.

Since we have a single group for study, we have to wait until the non exposed group get exposed to some factors and effect is created.so it is time consuming.

The number of exposures and outcomes can be studied simultaneously when we have two groups one exposed and the other non exposed.

A single group is selected for study,so the no. of persons involved are less in comparison with study with two groups. So it is cost effective.