Study Designs 1 and 2 Flashcards
What are the characteristics of a good study?
It is scientifically sound, valid, precise, and efficient
Look at it
Look at this until you know it.
What are the 3 types of descriptive study designs?
Case reports, case series, and cross sectional descriptive studies.
Analytical studies are designed to do what?
designed to test a hypothesis. Always compares groups.
What does a case report show?
That something can happen one.
Case studies and case reports are most often derived from where?
clinical practice.
What makes up a descriptive cross-sectional study?
a descriptive study that has a lot of study subjects (sample of the population at one point in time)
Does a descriptive cross sectional study calculate incidence or prevalence?
usually prevalence.
Can you generalize the results of a cross sectional study to a population?
Yes, if sampled correctly.
What are 2 types of analytical studies? What do analytical studies aim to do?
2 types: observational and experimenta. Analytical studies try to determine if an association exists and if so, how strong it is.
What are confounders?
3rd factors associated with both the exposure and the outcome, and that distort the association between exposure and outcome.
To evaluate a new vaccine for distemper, you vaccinate all dogs (1200) that enter your shelter in a 1 year period. None get distemper. What does this tell you about the effectiveness of this new vaccine?
Nothing.
Why are controls important?
They are essential for measuring the effect of exposures. They are the reference group that you make comparisons to.
How does an observational study differ from a descriptive study?
An observational study is an analytical study. An investigator is observing real-life situations and drawing inferences, and comparing one group to another. They take measurements, samples, ask questions, etc.
T/F: for both observational and experimental studies, subjects are first selected for the study. They are then allocated to a group, only if it is an observational study.
False. Subjects are allocated to groups only in experimental studies.
What factors play a role in subjects being selected for a study?
- they represent a population
- their exposure status
- their outcome status
T/F: Allocating subjects should not be a random process, so that you can make sure there are no confounding factors in your study.
FALSE. Allocation should always be a random process!
What is blinding?
When the researcher doesn’t know the treatment or exposure status of the subjects.
What is the problem with non-random sampling?
it may not represent the population or group.
What is the best study for demonstrating causality?
experimental studies.
Experimental studies are also known as?
Clinical trials, randomized controlled trials.
What are 2 types of observational studies?
ecological studies (populations are compared) and groups of individuals are compared.
T/F: measurements are made on individuals in eological studies.
False. They are all measured at a population level.
What are some drawbacks to ecological studies?
can’t describe causallity. You are measuring limited exposures, so there are lots of confounding factors. You are also not looking at individuals, and causality is measured at the individual level.
What type of observational study chooses study subjects because the have the outcome you are studying?
case control studies.
What observational study selects study subjects based on the exposure we are studying?
cohort studies.
What type of observational study chooses subjects to represent a population?
cross sectional studies?
When are individuals participating in analytical cross sectional studies classified into groups?
Once selected. They are selected regardless of their exposure or outcome status. This is measured once they are in the study, and the groups are then compared.
If you want to determine an association between outdoor activity and lyme dz in dogs, and you enroll 100 dogs w/ lyme dz, and 100 dogs w/o lyme dz, what type of study is this? Why?
case control study. Because you know the dz status before entering the subjects to the study.
What study is good in cases of outbreak investigation?
Case control studies.
What are the 2 types of cohort studies?
prospective and retrospective.
What is the difference between a retrospective cohort and a prospective cohort?
In a retrospective cohort, the outcome has already occurred. Retrospective cohorts go back in time, while prospective goes forward in time.
What are some downsides to prospective cohort studies?
they can take a long time and you have to deal with changing study populations.
What is a drawback to retrospective cohort studies?
they are not as good for establishing causality and you have to deal with recall bias.
