Study Designs 1 and 2 Flashcards Preview

RUSVM Epi Summer 2017 > Study Designs 1 and 2 > Flashcards

Flashcards in Study Designs 1 and 2 Deck (34)
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1
Q

What are the characteristics of a good study?

A

It is scientifically sound, valid, precise, and efficient

2
Q

Look at it

A

Look at this until you know it.

3
Q

What are the 3 types of descriptive study designs?

A

Case reports, case series, and cross sectional descriptive studies.

4
Q

Analytical studies are designed to do what?

A

designed to test a hypothesis. Always compares groups.

5
Q

What does a case report show?

A

That something can happen one.

6
Q

Case studies and case reports are most often derived from where?

A

clinical practice.

7
Q

What makes up a descriptive cross-sectional study?

A

a descriptive study that has a lot of study subjects (sample of the population at one point in time)

8
Q

Does a descriptive cross sectional study calculate incidence or prevalence?

A

usually prevalence.

9
Q

Can you generalize the results of a cross sectional study to a population?

A

Yes, if sampled correctly.

10
Q

What are 2 types of analytical studies? What do analytical studies aim to do?

A

2 types: observational and experimenta. Analytical studies try to determine if an association exists and if so, how strong it is.

11
Q

What are confounders?

A

3rd factors associated with both the exposure and the outcome, and that distort the association between exposure and outcome.

12
Q

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?

A

Nothing.

13
Q

Why are controls important?

A

They are essential for measuring the effect of exposures. They are the reference group that you make comparisons to.

14
Q

How does an observational study differ from a descriptive study?

A

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.

15
Q

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.

A

False. Subjects are allocated to groups only in experimental studies.

16
Q

What factors play a role in subjects being selected for a study?

A
  1. they represent a population
  2. their exposure status
  3. their outcome status
17
Q

T/F: Allocating subjects should not be a random process, so that you can make sure there are no confounding factors in your study.

A

FALSE. Allocation should always be a random process!

18
Q

What is blinding?

A

When the researcher doesn’t know the treatment or exposure status of the subjects.

19
Q

What is the problem with non-random sampling?

A

it may not represent the population or group.

20
Q

What is the best study for demonstrating causality?

A

experimental studies.

21
Q

Experimental studies are also known as?

A

Clinical trials, randomized controlled trials.

22
Q

What are 2 types of observational studies?

A

ecological studies (populations are compared) and groups of individuals are compared.

23
Q

T/F: measurements are made on individuals in eological studies.

A

False. They are all measured at a population level.

24
Q

What are some drawbacks to ecological studies?

A

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.

25
Q

What type of observational study chooses study subjects because the have the outcome you are studying?

A

case control studies.

26
Q

What observational study selects study subjects based on the exposure we are studying?

A

cohort studies.

27
Q

What type of observational study chooses subjects to represent a population?

A

cross sectional studies?

28
Q

When are individuals participating in analytical cross sectional studies classified into groups?

A

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.

29
Q

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?

A

case control study. Because you know the dz status before entering the subjects to the study.

30
Q

What study is good in cases of outbreak investigation?

A

Case control studies.

31
Q

What are the 2 types of cohort studies?

A

prospective and retrospective.

32
Q

What is the difference between a retrospective cohort and a prospective cohort?

A

In a retrospective cohort, the outcome has already occurred. Retrospective cohorts go back in time, while prospective goes forward in time.

33
Q

What are some downsides to prospective cohort studies?

A

they can take a long time and you have to deal with changing study populations.

34
Q

What is a drawback to retrospective cohort studies?

A

they are not as good for establishing causality and you have to deal with recall bias.