Lesson 3: Measures of Risk

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Self-Assessment Quiz

Now that you have read Lesson 3 and have completed the exercises, you should be ready to take the self-assessment quiz. This quiz is designed to help you assess how well you have learned the content of this lesson. You may refer to the lesson text whenever you are unsure of the answer.

Unless otherwise instructed, choose ALL correct choices for each question.

  1. Which of the following are frequency measures?
    1. Birth rate
    2. Incidence
    3. Mortality rate
    4. Prevalence
Use the following choices for Questions 2–4.
  1. Ratio
  2. Proportion
  3. Incidence proportion
  4. Mortality rate
  1. ____
    # women in Country A who died from lung cancer in 2004 divided by# women in Country A who died from cancer in 2004
  2. ____
    # women in Country A who died from lung cancer in 2004 divided by# women in Country A who died from breast cancer in 2004
  3. ____
    # women in Country A who died from lung cancer in 2004 divided byestimated # women living in Country A on July 1, 2004
  4. All proportions are ratios, but not all ratios are proportions.
    1. True
    2. False
  5. In a state that did not require varicella (chickenpox) vaccination, a boarding school experienced a prolonged outbreak of varicella among its students that began in September and continued through December. To calculate the probability or risk of illness among the students, which denominator would you use?
    1. Number of susceptible students at the ending of the period (i.e., June)
    2. Number of susceptible students at the midpoint of the period (late October/early November)
    3. Number of susceptible students at the beginning of the period (i.e., September)
    4. Average number of susceptible students during outbreak
  6. Many of the students at the boarding school, including 6 just coming down with varicella, went home during the Thanksgiving break. About 2 weeks later, 4 siblings of these 6 students (out of a total of 10 siblings) developed varicella. The secondary attack rate among siblings was, therefore,:
    1. 4 ⁄ 6
    2. 4 ⁄ 10
    3. 4 ⁄ 16
    4. 6 ⁄ 10
  7. Investigators enrolled 100 diabetics without eye disease in a cohort (follow-up) study. The results of the first 3 years were as follows:
    Year 1: 0 cases of eye disease detected out of 92; 8 lost to follow-up
    Year 2: 2 new cases of eye disease detected out of 80; 2 had died; 10 lost to follow-up
    Year 3: 3 new cases of eye disease detected out of 63; 2 more had died; 13 more lost to follow-up
    The person-time incidence rate is calculated as:
    1. 5 ⁄ 100
    2. 5 ⁄ 63
    3. 5 ⁄ 235
    4. 5 ⁄ 250
  8. The units for the quantity you calculated in Question 8 could be expressed as:
    1. cases per 100 persons
    2. percent
    3. cases per person-year
    4. cases per person per year
  9. Use the following choices for the characteristics or features listed below:
    1. Incidence
    2. Prevalence
    1. ____ Measure of risk
    2. ____ Generally preferred for chronic diseases without clear date of onset
    3. ____ Used in calculation of risk ratio
    4. ____ Affected by duration of illness
Use the following information for Questions 11–15.
Within 10 days after attending a June wedding, an outbreak of cyclosporiasis occurred among attendees. Of the 83 guests and wedding party members, 79 were interviewed; 54 of the 79 met the case definition. The following two-by-two table shows consumption of wedding cake (that had raspberry filling) and illness status.
Ill Well Total
Total 54 25 79
Ate wedding cake? Yes 50 3 53
No 4 22 26
Source: Ho AY, Lopez AS, Eberhart MG, et al. Outbreak of cyclosporiasis associated with imported raspberries, Philadelphia, Pennsylvania, 2000. Emerg Infect Dis 2002;l8:783–6.
  1. The fraction 54 ⁄ 79 is a/an:
    1. Food-specific attack rate
    2. Attack rate
    3. Incidence proportion
    4. Proportion
  2. The fraction 50 ⁄ 54 is a/an:
    1. Attack rate
    2. Food-specific attack rate
    3. Incidence proportion
    4. Proportion
  3. The fraction 50 ⁄ 53 is a/an:
    1. Attack rate
    2. Food-specific attack rate
    3. Incidence proportion
    4. Proportion
  4. The best measure of association to use for these data is a/an:
    1. Food-specific attack rate
    2. Odds ratio
    3. Rate ratio
    4. Risk ratio
  5. The best estimate of the association between wedding cake and illness is:
    1. 6.1
    2. 7.7
    3. 68.4
    4. 83.7
    5. 91.7
    6. 94.3
  6. The attributable proportion for wedding cake is:
    1. 6.1%
    2. 7.7%
    3. 68.4%
    4. 83.7%
    5. 91.7%
    6. 94.3%
Use the following diagram for Questions 17 and 18. Assume that the horizontal lines in the diagram represent duration of illness in 8 different people, out of a community of 700.
Line chart showing number of ill and recovered persons between July and August.
Image Description
  1. What is the prevalence of disease during July?
    1. 3 ⁄ 700
    2. 4 ⁄ 700
    3. 5 ⁄ 700
    4. 8 ⁄ 700
  2. What is the incidence of disease during July?
    1. 3 ⁄ 700
    2. 4 ⁄ 700
    3. 5 ⁄ 700
    4. 8 ⁄ 700
  3. What is the following fraction?
    Number of children < 365 days of age who died in Country A in 2004 divided byNumber of live births in Country A in 2004
    1. Ratio
    2. Proportion
    3. Incidence proportion
    4. Mortality rate
  4. Using only the data shown below for deaths attributed to Alzheimer’s disease and to pneumonia/influenza, which measure(s) can be calculated?
    1. Proportionate mortality
    2. Cause-specific mortality rate
    3. Age-specific mortality rate
    4. Mortality rate ratio
    5. Years of potential life lost
    Table 3.16 Number of Deaths Due to Alzheimer’s Disease and Pneumonia/Influenza — United States, 2002
    Age Group (years) Alzheimer’s
    disease    		 Pneumonia/
    Influenza
    < 5 0 373
    5–14 1 91
    15–24 0 167
    <34 32 345
    35–44 12 971
    45–54 52 1,918
    55–64 51 2,987
    65–74 3,602 6,847
    75–84 20,135 19,984
    85+ 34,552 31,995
    Total 58,866 65,681
    Source: Kochanek KD, Murphy SL, Anderson RN, Scott C. Deaths: Final data for 2002. National vital statistics reports; vol 53, no 5. Hyattsville, Maryland: National Center for Health Statistics, 2004.
  5. Which of the following mortality rates use the estimated total mid-year population as its denominator?
    1. Age-specific mortality rate
    2. Sex-specific mortality rate
    3. Crude mortality rate
    4. Cause-specific mortality rate
  6. What is the following fraction?
    Number of deaths due to septicemia among men aged 65–74 years in 2004 divided byEstimated number of men aged 65–74 years alive on July 1, 2004
    1. Age-specific mortality rate
    2. Age-adjusted mortality rate
    3. Cause-specific mortality rate
    4. Sex-specific mortality rate
  7. Vaccine efficacy measures are:
    1. The proportion of vaccinees who do not get the disease
    2. 1 − the attack rate among vaccinees
    3. The proportionate reduction in disease among vaccinees
    4. 1 − disease attributable to the vaccine
  8. To study the causes of an outbreak of aflatoxin poisoning in Africa, investigators conducted a case-control study with 40 case-patients and 80 controls. Among the 40 poisoning victims, 32 reported storing their maize inside rather than outside. Among the 80 controls, 20 stored their maize inside. The resulting odds ratio for the association between inside storage of maize and illness is:
    1. 3.2
    2. 5.2
    3. 12.0
    4. 33.3
  9. The crude mortality rate in Community A was higher than the crude mortality rate in Community B, but the age-adjusted mortality rate was higher in Community B than in Community A. This indicates that:
    1. Investigators made a calculation error
    2. No inferences can be made about the comparative age of the populations from these data
    3. The population of Community A is, on average, older than that of Community B
    4. The population of Community B is, on average, older than that of Community A

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