# Name(s): HW 2 (Chapters 5, 6 & the films & seminar on pandemics/Covid-19) due at 11:59 PM on Feb 25, 2021 (Friday) Total points =

Name(s):

HW 2 (Chapters 5, 6 & the films & seminar on pandemics/Covid-19) due at 11:59 PM on Feb

25, 2021 (Friday)

Total points = 100; show your work as much as you can to receive partial credit when needed.

You may work alone or in a group for this assignment. If this is a group assignment, turn in a

single assignment with all the names included.

Chapters 5 and 6 (75 points)

1. The

of a screening test is defined as the proportion of non-diseased

people who are correctly identified as "negative" by a screening test. (5 points)

a. Specificity

b. Sensitivity

C. Negative Predictive Value

d. Positive Predictive Value

2. Within the context of screening tests, people who do not have the disease and are

erroneously called "positive" by a test are called: (5 points)

a. False positives

b. True negatives

c. True positives

d. False negatives

3. A prostate-specific antigen (PSA) test is a quick screening test for prostate cancer. A

researcher wants to evaluate it using two groups. Group A consists of 131 men who had

biopsy-proven adenocarcinoma of the prostate while group B consists of 1,310 age- and

race-matched men all of whom showed no cancer at biopsy. The results of the PSA

screening test in each group is shown in the table:

True Numbers

Positive

Negative

Positive

110

786

PSA Test Results

Negative

21

524

How many people were given a false negative result? (5 points)

a. 545

b. 21

c. 110

d. 524 4. Use the table below to answer the following questions (10 points; 2.5 points each

question):

Reality

Disease

No Disease

Positive

5

2

Test

Negative

15

18

Test

20

20

a. is the sensitivity of this diagnostic test?

b. is the specificity of this diagnostic test?

c. is the positive predictive value of this diagnostic test?

d. is the negative predictive value of this diagnostic test?

5. Suppose the test in Question 4 is the first test in a sequential test. After this first test is

conducted, a second test is conducted on those tested positive in the first test. The

second test has 90% sensitivity and 90% specificity. is the net sensitivity and net

specificity of the sequential testing (10 points; 5 points each)?

Diseased

Not Diseased

Positive

Negative

5

2

7 6. Suppose the test in Question 4 is test 1 in a simultaneous test. Test 2 has sensitivity 90%

and specificity 90%. is the net sensitivity and net specificity of the simultaneous

testing (10 points; 5 points each)?

Reality

Disease

No Disease

Positive test

Negative test

20

20

40

Questions 7-9 are based on the following information:

Two raters were asked to classify 200 x-rays as positive or negative independently. The

comparison of their classification is shown in the following table (10 points):

Rater A

Rater B

Positive

Negative

Total

Positive

80

40

120

Negative

20

60

80

Total

100

100

200

7. The simple, overall percent agreement between the two people out of the total is (2

points):

a. 120/200 or 60%

b. 80/200 or 40%

c. 140/200 or 70%

d. 60/200 or 30%

8. The percent agreement by chance alone is (4 points):

a. 120/200 or 60%

b. 80/200 or 40%

c. 60/200 or 30%

d. 100/200 or 50% 9. The value of kappa is (4 points):

a. 20/50 or 0.40

b. 10/50 or 0.20

c. 20/40 or 0.50

d. 10/40 or 0.25

10. How does one interpret the kappa statistic (i.e., excellent vs. good vs. poor agreement)? (5

points)

11. One hundred eighty patients were treated for disease X from 1991 to 1993, and their

progress was followed to 1994. The treatment results are given in the table. No patients

were lost to follow-up.

NO. OF PATIENTS ALIVE

ON EACH ANNIVERSARY

Year of Treatment

No. of Patients Treated

1st

2nd

3rd

1991

75

60

56

48

1992

63

55

31

1993

42

37

Total

180

152

87

48

is the probability of surviving for all 3 years (5 points)?

12. Before reporting the results of a survival analysis, investigators compared baseline

characteristics of 38 people who withdrew from the study before its end to those who had

complete follow-up. This was done for which of the following reasons? (5 points) a. To test whether randomization was successful

b. To check for changes in treatment

c. To check whether those remaining in the study represent the total study

presentation

d. To check whether the survival estimate of those remaining in the study is the same

as the general population

e. To check that the survival estimate for those lost to follow-up is the same as the

general population

13. Based on the following Kaplan-Meier curve, what is the probability of surviving at the end of

the study? is the median survival time? (5 points; 2.5 points each):

Patient 1

Patient 2

Patient 3-

Patient 4-

Patient 5-

Lost to

follow-up

Patient 6

DIED

24

MONTHS SINCE ENROLLMENT Films & Seminar Questions on Pandemics & Covid-19 (25 points)

Questions 14-17 are based on the film, "We Heard the Bells-The Influenza of 1918" (10 points

total)

14. During seasonal influenza epidemics in the United States, there are certain groups that are

at higher risk of complications. Name three such groups. (3 points)

15. True or false: Influenza viruses have not caused a pandemic since 1918. (2 points)

a. True

b. False

16. True or false: The 1918 flu had as its most unique feature the fact that it had a high

propensity to kill young adults ages 15-40. (2 points)

a. True

b. False

17. Describe several things we learned from the 1918 influenza pandemic that still have

relevance today. ( 3 pts)

Questions 18-20 are based on the film, "Coronavirus: Race Against the Pandemic" (7 points

total)

18. True or false: the process of a virus jumping from one species to another is not a simple

one. (2 points)

a. True

b. False

19. Describe several reasons the SARS-CoV-2 virus was so much more deadly than the SARS

virus (another coronavirus) years earlier. (3 points)

20. In the conclusion of the film, Dr. Heymann says it’s wrong to think that medical science can

stop an outbreak. does he argue can stop an outbreak? (2 points) Questions 21-22 are based on the seminar recording, "Structural Racism & the Covid-19

Pandemic" (8 points)

21. True or false: There is some evidence that genetics is the basis for the racial health

disparities we’ve seen in Covid-19. (2 points)

a. True

b. False

22. is meant by "structural racism"? (3 points)

23. Describe several ways structural racism has impacted the effects of Covid-19 on

communities of color. (3 points)

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