Study Designs 1 and 2

Question 1

What are the characteristics of a good study?

Answer 1

It is scientifically sound, valid, precise, and efficient

Question 2

Look at it

Answer 2

Look at this until you know it.

Question 3

What are the 3 types of descriptive study designs?

Answer 3

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

Question 4

Analytical studies are designed to do what?

Answer 4

designed to test a hypothesis. Always compares groups.

Question 5

What does a case report show?

Answer 5

That something can happen one.

Question 6

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

Answer 6

clinical practice.

Question 7

What makes up a descriptive cross-sectional study?

Answer 7

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

Question 8

Does a descriptive cross sectional study calculate incidence or prevalence?

Answer 8

usually prevalence.

Question 9

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

Answer 9

Yes, if sampled correctly.

Question 10

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

Answer 10

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

Question 11

What are confounders?

Answer 11

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

Question 12

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?

Answer 12

Nothing.

Question 13

Why are controls important?

Answer 13

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

Question 14

How does an observational study differ from a descriptive study?

Answer 14

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.

Question 15

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.

Answer 15

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

Question 16

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

Answer 16

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

Question 17

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

Answer 17

FALSE. Allocation should always be a random process!

Question 18

What is blinding?

Answer 18

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

Question 19

What is the problem with non-random sampling?

Answer 19

it may not represent the population or group.

Question 20

What is the best study for demonstrating causality?

Answer 20

experimental studies.

Question 21

Experimental studies are also known as?

Answer 21

Clinical trials, randomized controlled trials.

Question 22

What are 2 types of observational studies?

Answer 22

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

Question 23

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

Answer 23

False. They are all measured at a population level.

Question 24

What are some drawbacks to ecological studies?

Answer 24

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.

Question 25

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

Answer 25

case control studies.

Question 26

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

Answer 26

cohort studies.

Question 27

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

Answer 27

cross sectional studies?

Question 28

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

Answer 28

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.

Question 29

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?

Answer 29

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

Question 30

What study is good in cases of outbreak investigation?

Answer 30

Case control studies.

Question 31

What are the 2 types of cohort studies?

Answer 31

prospective and retrospective.

Question 32

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

Answer 32

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

Question 33

What are some downsides to prospective cohort studies?

Answer 33

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

Question 34

What is a drawback to retrospective cohort studies?

Answer 34

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