PH 7711 Page 1 ________________
NAME: _________
PH 7711 Final Exam – Fall Semester 2021
Read each question carefully. Provide complete answer for full credit. Show your work where calculation is
involved. Good luck.
Part 1. (10 points)
A study was conducted to investigate the functional impairment outcome of children served by systems of care.
Data were collected on children age 3 to 18 years using the Columbia Impairment Scale (CIS). Which of the
following variables describe the appropriate measurement scale or type? Indicate whether the variable is
Continuous, Ordinal, Nominal, or Dichotomous.
Variable Type
1. Age of the child
2. Gender of the child
3. Type of service (1=System of Care; 0=Other)
4. Functional impairment score (range=0-52)
5. Caregiver’s income
Part 2. (30 points)
You have two tests available. The first, called TESTER, has a sensitivity of 50% and a specificity of
50%. The second, called DECIDER, has a sensitivity of 100% and a specificity of 100%.
You want to test a population of 1000 persons who have a prevalence of 50% for the condition of
interest to you. You decide to use TESTER first, and confirm the positives with DECIDER. You run
TESTER and get the following results (fill in the blanks)
Number of true positives you find
Number of false positives you find
Positive predictive value for TESTER
You run DECIDER and get the following results (fill in the blanks)
Number of specimens tested
Prevalence among the specimens tested
Number of true positives
Number of false positives
Positive predictive value for DECIDER
1
, PH 7711 Page 2 ________________
NAME: _________
The hidden cost of this strategy is the number of False Negatives that get lost. (These are people whose
screening test is negative, who think they don’t have the disease, and who may turn up sick later on.)
Number of False Negative tests that this
screening strategy will create
1. Based on these results, and leaving aside issues of cost, which of the following would be the best screening
strategy:
a. Use TESTER first, the DECIDER.
b. Use DECIDER first, then TESTER.
c. Use DECIDER and don’t use TESTER at all.
d. Find a better test.
Answer: ________
2. A screening test for SARS-CoV-2 (Covid-19) used to test the presence of positive antibody positive or
negative antibody using the Antigen test (rapid test) showed 95% sensitivity and 98% specificity? The
prevalence rate of the disease is 20%.
a. Interpret the two results (sensitivity and specificity).
b. Calculate the PPV and interpret.
2
NAME: _________
PH 7711 Final Exam – Fall Semester 2021
Read each question carefully. Provide complete answer for full credit. Show your work where calculation is
involved. Good luck.
Part 1. (10 points)
A study was conducted to investigate the functional impairment outcome of children served by systems of care.
Data were collected on children age 3 to 18 years using the Columbia Impairment Scale (CIS). Which of the
following variables describe the appropriate measurement scale or type? Indicate whether the variable is
Continuous, Ordinal, Nominal, or Dichotomous.
Variable Type
1. Age of the child
2. Gender of the child
3. Type of service (1=System of Care; 0=Other)
4. Functional impairment score (range=0-52)
5. Caregiver’s income
Part 2. (30 points)
You have two tests available. The first, called TESTER, has a sensitivity of 50% and a specificity of
50%. The second, called DECIDER, has a sensitivity of 100% and a specificity of 100%.
You want to test a population of 1000 persons who have a prevalence of 50% for the condition of
interest to you. You decide to use TESTER first, and confirm the positives with DECIDER. You run
TESTER and get the following results (fill in the blanks)
Number of true positives you find
Number of false positives you find
Positive predictive value for TESTER
You run DECIDER and get the following results (fill in the blanks)
Number of specimens tested
Prevalence among the specimens tested
Number of true positives
Number of false positives
Positive predictive value for DECIDER
1
, PH 7711 Page 2 ________________
NAME: _________
The hidden cost of this strategy is the number of False Negatives that get lost. (These are people whose
screening test is negative, who think they don’t have the disease, and who may turn up sick later on.)
Number of False Negative tests that this
screening strategy will create
1. Based on these results, and leaving aside issues of cost, which of the following would be the best screening
strategy:
a. Use TESTER first, the DECIDER.
b. Use DECIDER first, then TESTER.
c. Use DECIDER and don’t use TESTER at all.
d. Find a better test.
Answer: ________
2. A screening test for SARS-CoV-2 (Covid-19) used to test the presence of positive antibody positive or
negative antibody using the Antigen test (rapid test) showed 95% sensitivity and 98% specificity? The
prevalence rate of the disease is 20%.
a. Interpret the two results (sensitivity and specificity).
b. Calculate the PPV and interpret.
2
