The Obstacle Course


Man Jumping a Hurdle

Questions to test your understanding

 

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When investigators gathered data on the number of motor vehicles in use over time, they found that the increase correlated strongly with the increase in lung cancer mortality. The correlation is evidence of an association between motor vehicle use and lung cancer mortality. Does this indicate that motor vehicle use is a cause of lung cancer mortality?

 
 
 
 

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A sample of 100 middle aged and elderly women was followed prospectively for 10 years in order to study rates of ovarian cancer. All subjects entered the study on January 1, 1990, and all were free of cancer at the beginning. All women were followed until December 31, 1999. None were lost to follow-up. During this period, five subjects were diagnosed with ovarian cancer, but they all survived to the end of the study.

Case #1 was diagnosed with ovarian cancer in January 1991.

Case #2 was diagnosed in January 1992.

Case #3 was diagnosed in January 1993.

Case #4 was diagnosed in January 1986.

Case #5 was diagnosed in January 1996.

The time at which these 5 subjects developed cancer is shown in this table: 

Use this information and the information in the table below to answer the questions beneath the tabl:

Subject

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

Case #1

 

cancer

 

 

 

 

 

 

 

 

Case #2

 

 

cancer

 

 

 

 

 

 

 

Case #3

 

 

 

 cancer

 

 

 

 

 

 

Case #4

 

 

 

 

 

 

 cancer

 

 

 

Case #5

 

 

 

 

 

 

 

 

cancer

 

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What was the incidence rate of ovarian cancer?

 
 
 
 

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Using the table in the question above, what was the prevalence of ovarian cancer on December 31, 1999?

 
 
 
 

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To calculate the cumulative incidence one assumes that all subjects had the same follow-up time at risk.

 
 

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A cohort study is conducted to determine whether smoking is associated with an increased risk of bronchitis in adults over the age of 40. The findings are as follows:

- The frequency of bronchitis in the smokers is 27 per 1,000 person-years.

- The frequency of bronchitis in the non-smokers is 3 per 1,000 person-years.

 What kind of measures of disease frequency are these?

 
 
 
 
 

Thinking man icon. There are 6 questions to answer below the table and other information

Use this information and the information in the table below to answer the questions beneath the table:

In January of 1990, 1,010 young adults offered to participate in a 10-year prospective study to determine their risk of Type-I diabetes.  This group underwent an initial blood test to determine whether they were diabetic, and eligible subjects were re-tested yearly for the next 10 years. Among the group that offered to join the study:

 ?  = Lost to follow-up        + = Blood test positive for diabetes         ------ = Continued disease-free follow-up 

Subject #

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

1

------

------

+

 

 

 

 

 

 

 

2

------

------

------

------

------

------

------

------

------

+

3

------

------

------

------

------

------

------

+

 

 

4

------

+

 

 

 

 

 

 

 

 

5

------

------

------

------

+

 

 

 

 

 

6

------

------

+

 

 

 

 

 

 

 

7

------

------

------

------

?

 

 

 

 

 

8

------

------

------

------

------

?

 

 

 

 

 

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In the group that was eligible for study, what was the cumulative incidence of diabetes from 1990 to 1999?

 
 
 
 

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Using the table for the preceding question what was the incidence rate of diabetes from 1990 to 1999?

 
 
 
 

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Suppose that the prevalence of "raspberry freckle syndrome" is 40 per 100,000 population, and the incidence of this syndrome is 20 per 100,000 person-days. What is the average duration of this syndrome?

 
 
 
 
 

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To determine the prevalence of the flu in Boston over a calendar year, you can multiply the incidence rate by the duration of the study period.

 
 

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To determine the incidence rate, which one of the following variables is NOT needed?