49 notecards = 13 pages (4 cards per page)
Descriptive Studies (limitations)
can not infer causality
Descriptive Studies are used to (5 things)
Descriptive studies measure
Social, economic and health conditions of population such as birth and death information (vital statistics).
Difference between Descriptive and Analytical Studies
Descriptive can provide a hypothesis
Descriptive Studies summary
Three types of Descriptive Studies
Ecologic Study (also known as Correlational Study).
Examine populations / groups rather than individuals.
Eco studies are
good to get general picture and infer additional studies for risk factors but care must be taken to not infer population results to the individual
Inaccurate inference from population or community results to the individual
Case Study definition
Report by individual or groups of individuals with specific conditions; no control group used.
Purpose of a case study
Often used to identify the beginning or presence of an epidemic or unusual outbreak.
Limitation of a case Study
Cannot be used to establish formal statistical association.
Prospective Case Study
Subjects included in study as they occur or are found meeting the criteria for inclusion.
Subjects are selected because historical records meet established criteria.
Case (series) study
Can also be prospective or retrospective by tracking groups of patients with a known exposure and/or treatment into the future to examine outcome of examine records for exposure and outcome
Results include all members of the study
Only select participant included in the results
Problem with case study/series
Case study and case series studies are subject to confounding by selection bias which limits inference on causality
Cross Sectional Study
Observes a population of interest at a single point in time or during a specific time interval.
Purpose of a cross sectional study
Examines the relationship between diseases (or other events) and possible associated factors as they exist in the population at one point in time.
Limitations of a cross sectional study
Healthy Worker Effect (workers seem to have lower morbidity/mortality rates because left work due to disability or death and therefore not included in study).
Most common form of a cross sectional study
Sampling schemes for cross sectional study (2 types)
PROBABILITY SAMPLE & NON-PROBABILITY SAMPLE
Definition of a probability sample and the 3 types
Is sample where everyone in the population has a “non-zero” chance of being included (in other words, everyone has a chance of being included!)
simple random sample
Everyone in population has equal chance of being selected (community survey, census, etc.).
Subjects are selected based on some established scheme
A pre-established (calculated) number of subjects are randomly selected from subsets of the total population (CNA).
Non probability sample definition and 3 types
Probability sampling is best for large-scale studies, non-probability approaches are best for complex or rare events.
Researchers choose subjects based on who they think would be most appropriate for the study; used when specific issue is being studied.
Convenience or acidental sampling
Samples are chosen based on accessibility (friends, mall shoppers, etc.); prone to bias.
A quota is established and subjects chosen until quota is met (65% male); often not representative.
1. What is an example of ecologic fallacy?
What is/are the limitation(s) of a cross-sectional study?
3. What is the main difference between Descriptive and Analytic studies?
4. Which of the following is not a descriptive study?
5. A study examining the effects of a nearby waste disposal site sampled every fifth house in a series of neighborhoods. This is an example of what type of sampling?
6. Non-probability samples are best used for:
7. What are case-studies/case series MOST used for?
8. What study design can incorporate consecutive and non consecutive participants?
9. What is/are the advantage(s) of a cross-sectional study?
10. Which of the following is a cross sectional study?
11. To study the association between knowledge and behaviors related to HIV in high school students, a questionnaire to assess knowledge about prevalence, causes and individual susceptibility to HIV and practice of risky sexual behaviors was administered.
A study that examines the death rates from colon cancer in each of the 50 U.S states in relation to the average percentage of residents in each state undergoing colonoscopy screening. This is an example of :
13. A study comparing the prevalence of cardiovascular disease in the US with the prevalence of cardiovascular disease in Japan is an example of _____
14. Which of the following is a cross sectional study?
15. A study describing the 5cases of West Nile Virus disease in Tarrant County in 2012 is an example of _____
15. A researcher set out to investigate the relationship between three major allergic diseases, asthma, allergic rhinitis (AR), and atopic dermatitis (AD), and psychological and behavioral problems in preschoolers. He conducted a survey using a modified International Study of Asthma and Allergies in Childhood questionnaire to determine the prevalence of symptoms and diagnosed allergic diseases, and a Korean version of the Child Behavior Checklist to assess internalizing, externalizing, and sleep problems among 780 preschoolers. This is a ____study design.
16. A study describing the prevalence of childhood obesity in Fort Worth is a Cross-Sectional study.