1) Which of the following is an example of an observational cohort study that might be used to assess the association between agent X and disease Y? (Select one)

a. A group of individuals exposed to agent X are recruited in 1995 and followed until 2004 at which time they are tested for the presence of disease Y.

b. A group of individuals with disease Y and without disease Y are recruited and interviewed about exposure to agent X in 2004.

c. A group of individuals exposed to agent X and a group of individuals not exposed to agent X are recruited and tested for disease Y in 1995.

d. A group of individuals with disease Y and without disease Y are recruited in 2004 and their past health records screened for documentation of exposure to agent X in 1995

e. A group of individuals without disease Y are recruited in 2004 and their past health records screened for documentation of exposure to agent X in 1995

2) Use the following information for questions 2 and 3:

Two tests (A and B) for osteoporosis have the following characteristics:

• Test A has a sensitivity of 60% and a specificity of 80%.
• Test B has a sensitivity of 90% and a specificity of 90%.

A nurse first uses Test A. Patients who test positive on Test A are then given Test B. Testing positive on both tests is diagnostic of osteoporosis. What is the net sensitivity of this testing approach?(Select one)

a. 54%

b. 65%

c. 82%

d. 90%

e. 98%

3) If the nurse reversed the order of the testing (i.e. used Test B first and the administered Test A to those who were positive on Test B), what would happen to the net specificity?(Select one)

a. decrease

b. stay the same

c. increase

d. not enough information to tell