Assignment 4


General Instructions:

  1. Add your answers after each question in BOLD FONT.
  2. Make sure that your responses are succinct and directly related to the question. Your responses to questions in Parts 2 through 5 should be only 1-4 sentences in length.


Part 1. 

Complete the table to describe epidemiologic study designs.  Name the study design that is described and list ONE (1) strength, ONE (1) limitation, and ONE (1) measure of either frequency OR comparison that could be used in the analysis for the given study design.

Description Study Design Type

(1 point)

1 Strength

(1 point)

1 Limitation

(1 point)

1 Measure of Frequency OR Comparison Used in Analysis

(1 point)

1.        One or more groups of people are identified based on exposure and followed over time to assess differences in the frequency of a health outcome and determine the relationship between the exposure and the outcome        
2.        Researcher manipulates the exposure, assigning participants to exposed and unexposed groups, following them over time to assess differences in the frequency of a health outcome and determine the relationship between the exposure and the outcome        
3.        Compares people with a health outcome to those who do not have the health outcome and looks back retrospectively to compare how frequently the exposure to a risk factor is present in each group to determine the relationship between the risk factor and the disease.        
4.        Data on existing exposures and health outcomes collected from a population at a single point in time.        
  1. Many hair dyes contain substances that are suspected human carcinogens. Consequently, several investigations have attempted to assess the risk of cancer among beauticians and others frequently exposed to hair dyes.  One study based on death certificate data found that among a group of cases who died of lung cancer and a set of controls matched on age, sex, and race that died of causes other than cancer, beauticians had six times the risk of dying of pulmonary malignancy compared to people in other professions (OR = 6.0). The researchers did not control for cigarette smoking.  Describe how smoking cigarettes could act as a confounder in the relationship observed between being a beautician and lung cancer.  (Hint – refer to the general rule for confounding) (2 points)


Part 2.

For each of the following research hypotheses, answer the following questions:

  • What is the MOST IDEAL(strongest evidence) epidemiologic study design to address the hypothesis?
  • Why?


  1. Contaminated egg salad at a deli caused an outbreak of severe gastrointestinal disease. (2 points)



  1. Low birthweight causes adult-onset asthma. (2 points)



  1. Prenatal cocaine exposure affects later child cognitive performance. (2 points)



  1. Gene polymorphisms are associated with Type 1 diabetes. (2 points)



  1. Milk intake midlife is protective for the development of late-onset dementia at >70 years of age. (2 points)


Part 5. 

It may be difficult to accurately estimate the prevalence of depression in the general population, even in high income countries.  Studies face issues of selection bias and information bias in their estimates of depression.  Read the following research scenarios.  For each, describe one way selection bias may affect the estimate of depression and one way information bias may affect the estimate of depression.  Indicate whether the bias you have identified could over- or underestimate the prevalence of depression in the general population.

  1. A research study tries to estimate the prevalence of depression in a general population by collecting data diagnosis information from medical records at a primary care physician office. (2 points)


Selection bias:



Information bias:



  1. A research study tries to estimate the prevalence of depression in the general population by surveying a member of a household through a telephone interview. (2 points)


Selection bias:



Information bias:


Part 6

On the morning of March 11, the Texas Department of Health (TDH) in Austin received a telephone call from a student at a university in south-central Texas.  The student reported that he and his roommate, a fraternity brother, were suffering from nausea, vomiting, and diarrhea. Both had become ill during the night.  The roommate had taken an over-the-counter medication with some relief of his symptoms.  Neither the student nor his roommate had seen a physician or gone to the emergency room. The students believed their illness was due to food they had eaten at a local pizzeria the previous night.  They asked if they should attend classes and take a biology midterm exam that was scheduled that afternoon.


TDH staff were skeptical of the student’s report but felt that a minimal amount of exploration was necessary.  They began by making a few telephone calls to establish the facts and determine if other persons were similarly affected.  The pizzeria, where the student and his roommate had eaten, was closed until 11:00 A.M.   There was no answer at the University Student Health Center, so a message was left on its answering machine.


A call to the emergency room at a local hospital (Hospital A) revealed that 23 university students had been seen for acute gastroenteritis in the last 24 hours.  In contrast, only three patients had been seen at the emergency room for similar symptoms from March 5-9, none of whom were associated with the university.

At 10:30 A.M., the physician from the University Student Health Center returned the call from TDH and reported that 20 students with vomiting and diarrhea had been seen the previous day. He believed only 1-2 students typically would have been seen for these symptoms in a week. The Health Center had not collected stool specimens from any of the ill students.


By March 12, seventy-five persons with vomiting or diarrhea had been reported to TDH.  All were students who lived on the university campus.  No cases were identified among university faculty or staff or from the local community.


  1. How would you design an epidemiological investigation to research the cause of this outbreak? Give pertinent information to describe your study design, including an overview of how the study would be conducted, study population, exposure definition and data collection, outcome definition and data collection, and analysis. (5 points)

Last Updated on March 25, 2018 by Essay Pro