Review Questions-association And Bias

Estimating Risk: Is There an Association?

Dept.Epidemiology Ben Fu Yang 1

1.  Of 2,872 persons who had received radiation treatment in childhood because of an enlarged thymus, cancer of the thyroid developed in 24 and a benign thyroid tumor developed in 52. A comparison group consisted of 5,055 children who had received no such treatment (brothers and sisters of the children who had received radiation treatment). During the follow-up period, none of the comparison group developed thyroid cancer, but benign thyroid tumors developed in 6. Calculate the relative risk for benign thyroid tumors: _____   

2

2.  In a study of a disease in which all cases that developed were ascertained, if the relative risk for the association between a factor and the disease is equal to or less than 1.0, then:   a.  There is no association between the factor and the disease   b.  The factor protects against development of the disease   c.  Either matching or randomization has been unsuccessful   d.  The comparison group used was unsuitable, and a valid comparison is not possible   e.  There is either no association or a negative association between the factor and the disease 3

Questions 3 and 4 are based on the information given in the following table. In a small pilot study, 12 women with uterine cancer and 12 with no apparent disease were contacted and asked whether they had ever used estrogen. Each woman with cancer was matched by age, race, weight, and parity to a woman without disease. The results are shown below:

4

Pair Women with Uterine No. Cancer

Women without Uterine Cancer

1 2 3 4 5 6 7 8 9 10 11 12

Estrogen nonuser Estrogen nonuser Estrogen user Estrogen user Estrogen nonuser Estrogen nonuser Estrogen nonuser Estrogen nonuser Estrogen user Estrogen user Estrogen nonuser Estrogen nonuser

Estrogen user Estrogen nonuser Estrogen user Estrogen user Estrogen user Estrogen nonuser Estrogen user Estrogen user Estrogen nonuser Estrogen nonuser Estrogen user Estrogen user

5

3

3.What is the estimated relative risk of cancer when analyzing this study as a matched-pairs study? a.  0.25  b.  0.33  c.  1.00  d.  3.00  e.  4.20 4.  Unmatch the pairs. What is the estimated relative risk of cancer when analyzing this study as an unmatched study design? a.  0.70  b.  1.43  c.  2.80  d.  3.00  e.  4.00 6

Questions 5 through 7 are based on the following information. Talbot and colleagues carried out a study of sudden unexpected death in women. Data on smoking history are shown in the following table. Smoking History for Cases of ASHD Sudden Death and Controls (Current Smoker, 1+ Pack/Day) [Matched Pairs], Allegheny County, 1980

Cases Smoking 1+ pack/day Smoking <1 pack/day Total

CONTROLS Smoking 1+ Smoking <1 Pack/Day Pack/Day

Total

2

36

38

8

34

42

10

70

80

7

5.Calculate the matched-pairs odds ratio for these data. ____ 6.Using data from the table, unmatch the pairs and calculate an unmatched odds ratio. _____

7.What are the odds that the controls smoke 1+ pack/d

8

Questions 8 and 9 are based on the information given bellow.

Rates of Atherosclerotic Heart Disease (ASHD) per 10,000 Population, By Age and Sex, Framingham, Massachusetts MEN Age at Begin ning of Study (yr)

WOMEN

ASHD Yearly FollowRates up Exams at (Mean Initial Annual Exam Incidence)

ASHD Yearly FollowRates up Exams at (Mean Initial Annual Exam Incidence)

29–34

76.7

19.4

0.0

0.0

35–44

90.7

40.0

17.2

2.1

45–54

167.6

106.5

111.1

29.4

55–62

505.4

209.1

211.1

117.8

9

8.The relative risk for developing ASHD subsequent to entering this study in men as compared to women is: a.Approximately equal in all age groups b.Highest in the oldest age group c.Lowest in the youngest and oldest age groups, and highest at ages 35–44 and 45–54 years d.Highest in the youngest and oldest age groups, and lowest at ages 35–44 and 45– 54 years e.Lowest in the oldest age group 10

9.The most likely explanation for the differences in rates of ASHD between the initial examination and the yearly follow-up examinations in men is: a.The prevalence and incidence of ASHD increase with age in men b.Case-fatality rates of ASHD are higher at younger ages in men c.A classic cohort effect explains these results d.The case-fatality rate in ASHD is highest in the first 24 hours following a heart attackinitial examination measures the e.The prevalence of ASHD, whereas the subsequent examinations primarily measure the incidence of ASHD

11

1.Which of the following is an approach to handling confounding? a.Individual matching b.Stratification c.Group matchingd.Adjustment e.All of the above 2.It has been suggested that physicians may examine women who use oral contraceptives more often or more thoroughly than women who do not. If so, and if an association is observed between phlebitis and oral contraceptive use, the association may be due to: a.Selection biasb.Interviewer biasc.Surveillance bias d.Nonresponse bias e.Recall bias

12