Select the most appropriate study design for each of the following questions. (Note: All study design options may not be used and each design option can be used more than once.

1. A study is done to examine the association between a mother’s education and risk of a congenital heart defect in her offspring. The investigator enrolls a group of mothers of babies with birth defects and a group of mothers of babies without birth defects. The mothers are then asked a series of questions about their education.

Case series
Case-control study
Nested case-control study
Prospective cohort study
Retrospective cohort study
Randomized clinical trial
Cross-sectional study
Ecological study
Case cohort study
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2. A study on the association of coffee consumption and performance on a memory test randomly assigns half of the enrolled subjects to drink coffee one hour before taking the memory test and the other half to not drink coffee one hour before taking the memory test.

Case series
Case-control study
Nested case-control study
Prospective cohort study
Retrospective cohort study
Randomized clinical trial
Cross-sectional study
Ecological study
Case cohort study
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3. A study examining the association between meat consumption and heart disease compares the average number of kilograms of meat consumed per person for 50 different countries to the incidence rate of heart disease in the same 50 countries.

Case series
Case-control study
Nested case-control study
Prospective cohort study
Retrospective cohort study
Randomized clinical trial
Cross-sectional study
Ecological study
Case cohort study
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4. An investigator enrolls a group of healthy individuals and distributes questionnaires to collect information on sex and blood type. The investigator then examines the association between sex and blood type.

Case series
Case-control study
Nested case-control study
Prospective cohort study
Retrospective cohort study
Randomized clinical trial
Cross-sectional study
Ecological study
Case cohort study
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5. A study describes a group of hospital patients all of whom suffer from migraine with aura and experienced an ischemic stroke.

Case series
Case-control study
Nested case-control study
Prospective cohort study
Retrospective cohort study
Randomized clinical trial
Cross-sectional study
Ecological study
Case cohort study
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6. A study recruits a group of college graduates. At the time of recruitment, participants provide a blood sample that is immediately stored and they complete a questionnaire about lifestyle behaviors. The participants are followed over time to see who develops Parkinson’s Disease. Two studies are performed. Classify each study.

a) In one study, the researchers compare people reporting regular physical activity to those who are sedentary.

Case series
Case-control study
Nested case-control study
Prospective cohort study
Retrospective cohort study
Randomized clinical trial
Cross-sectional study
Ecological study
Case cohort study
b) In another study, the stored blood sample for each case is compared to the blood sample for a non-case that was alive and at risk on the day that the case was diagnosed with Parkinson's disease. The blood samples are analyzed to see if serum levels of Vitamin D are associated with the risk of developing Parkinson’s disease.

Case series
Case-control study
Nested case-control study
Prospective cohort study
Retrospective cohort study
Randomized clinical trial
Cross-sectional study
Ecological study
Case cohort study
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7. A researcher uses a database of medical records to identify a group of retired factory workers. He reviews each person’s medical records to follow their factory exposures over time and see which of these subjects has developed skin cancer in the past 25 years.

Case series
Case-control study
Nested case-control study
Prospective cohort study
Retrospective cohort study
Randomized clinical trial
Cross-sectional study
Ecological study
Case cohort study

please answer this qus

1. Case-control study

Explanation: In this study design, the investigator enrolls a group of mothers of babies with birth defects (cases) and a group of mothers of babies without birth defects (controls) and then collects data on their education. The purpose is to examine the association between a mother's education and the risk of a congenital heart defect in her offspring.

2. Randomized clinical trial
Explanation: This study design randomly assigns half of the enrolled subjects to drink coffee one hour before taking the memory test and the other half to not drink coffee. The purpose is to examine the association of coffee consumption and performance on a memory test.

3. Ecological study
Explanation: This study design compares the average number of kilograms of meat consumed per person for 50 different countries to the incidence rate of heart disease in the same 50 countries. The purpose is to examine the association between meat consumption and heart disease at a population level.

4. Cross-sectional study
Explanation: In this study design, the investigator collects information on sex and blood type from a group of healthy individuals at a single point in time. The purpose is to examine the association between sex and blood type.

5. Case series
Explanation: This study design describes a group of hospital patients who all suffer from migraine with aura and experienced an ischemic stroke. The purpose is to describe the characteristics of this specific group of patients.

6a. Prospective cohort study
Explanation: In this study, a group of college graduates are recruited and followed over time to see who develops Parkinson's Disease. The researchers compare people reporting regular physical activity to those who are sedentary. The purpose is to examine the association between physical activity and the development of Parkinson's Disease.

6b. Nested case-control study
Explanation: In this study, stored blood samples for each case (individuals diagnosed with Parkinson's Disease) are compared to the blood samples for non-cases (individuals who were alive and at risk on the day that the case was diagnosed) to see if serum levels of Vitamin D are associated with the risk of developing Parkinson's Disease.

7. Retrospective cohort study
Explanation: In this study design, the researcher uses a database of medical records to identify a group of retired factory workers. The researcher reviews each person's medical records to follow their factory exposures over time and determine which subjects have developed skin cancer in the past 25 years. The purpose is to examine the association between factory exposures and the development of skin cancer.