This is an individual homework assignment.  While you are allowed to use any notes, textbooks or readings, and to consult with the faculty instructor, if having trouble, you are expected to think through this assignment and do it on your own without the collaboration of classmates.  You should wait until after you have listened to Lectures #13, 14, 15 and 16, and read pages 153-158 of the textbook before starting this homework assignment. Remember to have your notes in front of you while doing this homework. 

Absolutely no late homework assignments will be accepted.  Please type your answers, numbering all of the questions. 

Part 1: Neural Tube Defects and Multivitamins (11 points in total)

In 1988 Joseph Mulinare and his fellow investigators reported their findings concerning the association of neural tube defects (type of birth defects) and periconceptional use of multivitamins (taking multivitamins around the time they became pregnant) (JAMA 1988; 260: 3141-3145).  They selected several groups of infants.  One group consisted of “all live-born or stillborn infants with a diagnosis of anecephaly or spina bifida (the two major kinds of neural tube defects) born during the years 1968 through 1980 who were registered in the Metropolitan Atlanta Congenital Defects Program.”  The second group consisted of “live-born babies without birth defects who were randomly chosen from all live births that occurred in the metropolitan Atlanta surveillance area.”  Data on multivitamin use was then obtained.  Multivitamin use was defined as “multivitamin or prenatal vitamin consumption during every month of the entire six month period …from three months before conception through the third month of pregnancy by the mother.”  The following table presents partial results from that report. (A number of changes and adjustments have been made to simplify the table for purposes of this example.)

2 by 2 Table for Maternal Multivitamin Use and Neural Tube Defects

	Infant born with Neural Tube Defect	Infant not born with birth defect	Total
Mother took multivitamins	24	411	435
Mother did not take multivitamins	159	1092	1251
Total	183	1503	1686

1. What is the exposure in this study? (1 point)
2. What is the disease outcome in this study? (1 point)
3. According to the description above, what were the two comparison groups? (2 points)
4. Were the two comparison groups those with and without the outcome or those with and without the exposure?  (1 point)
5. What type of study design is this?  (Choose either case-control or cohort.) (1 point)
6. If this is a cohort study, calculate a relative risk.  If it is a case-control study, calculate an odds ratio.  Calculate only the one that goes with this study design, and state which one it is.  Show all steps, including the formula, numerator and denominator.  Round off the final answer to two places after the decimal. (3 points)
7. Is taking multivitamins around the time of conception a possible protective or risk factor for having a child with neural tube defects? (1 point)
8. Is taking multivitamins strongly associated with neural tube defects (i.e.  a strong risk factor or a strong protective factor) or is it just weakly associated?  (Hint: consider a strong risk factor as being an odds ratio or relative risk > 2.00, and a strong protective factor as an odds ratio or relative risk < 0.5.) (1 point)

Part 2:  Maternal Drug Consumption and Birth Defects (12 points in total)

As an epidemiologist you are going to investigate the effect of a drug suspected of causing malformations in newborn infants when the drug in question is taken by pregnant women during the course of their pregnancies. As your sample, you will use the next 250 single births occurring in a given hospital. You will follow these mothers during the entire course of their pregnancies, maintaining a complete and accurate record of drug use during pregnancy.  This will be achieved not only through interviewing the women, but in addition, you will review medical records to verify use of the drug.  At the end of the study, the resultant data turn out to be:  Fifty mothers have taken the suspected drug during their pregnancies. Of these mothers, 42 have delivered malformed infants. In addition, there are 15 other infants born with malfunctions to women who have not taken the drug.

1. What is the exposure in this study? (1 point)
2. What is the disease outcome in this study? (1 point)
3. What type of study design is this?  (Choose either case-control or cohort.) (1 point)
4. Explain how you know that it is this study design. (2 points)
5. Construct a two by two table with all labeled columns and rows, including totals for this study. (2 points)
6. If this is a cohort study, calculate a relative risk.  If it is a case-control study, calculate an odds ratio.  Calculate only the one that goes with this study design, and state which one it is.  Show all steps, including the formula, numerator and denominator.  Round off the final answer to two places after the decimal. (3 points)
7. Is the exposure possible protective or risk factor for the outcome? (1 point)
8. Is the exposure strongly associated with the outcome (i.e.  a strong risk factor or a strong protective factor) or is it just weakly associated?  (Hint: consider a strong risk factor as being an odds ratio or relative risk > 2.00, and a strong protective factor as an odds ratio or relative risk < 0.5.) (1 point)

Part 3:  Study Design Identification (20 points in total, 2 points each)

For each of the descriptions below, identify the study design. Choose only one study design per description: ecologic, cross-sectional, case-control, or cohort study.  Write the type of study design that applies below each description.

Example:

1. The level of unemployment was used as a measure of economic distress in Germany.  Researchers examined the association between economic distress and general anxiety syndrome across states in Germany.

Study Design: Ecologic

Study Design:

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