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Flashcards in 7: Evidence based medicine 2 Deck (20)
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1

What is a cohort study?

Comparisons of groups of a population who were a) exposed b) not exposed to a certain thing

e.g those exposed to radiation after Hiroshima/Nagasaki atomic bombings

2

In a cohort study, you start with a population with different incidences of a thing and work (forwards / backwards) to figure out what caused this difference.

backwards

3

In a cohort study, you can either

a) start with a population and follow them going forwards

b) go back and examine differences in a population

What are these types of study called?

Prospective cohort study

Retrospective cohort study

4

A cohort study allows you to estimate the ___ of something occuring in a population.

risk

5

In a cohort study, the population you have needs to be a ___ population.

general

otherwise you don't know what's typical/rare

6

What size of population do you need to pick up rare diseases in a cohort study?

Large sample size

7

What is relative risk?

Relative risk = Probability of event (incidence) when exposed / Probability of event (incidence) when not exposed

8

What is relative risk also known as?

Risk ratio

9

When there is no difference between two populations, the relative risk is _.

1

10

If the risk ratio is < 1, the exposed population are (protected from / vulnerable to) the effect.

protected from

11

If the risk ratio is > 1, the exposed population is (protected from / vulnerable to) the effect.

vulnerable to

12

What is absolute risk?

Absolute risk = Risk in exposed group - Risk in non-exposed group

13

What is a case control study?

Find two populations, one with the condition and one not

Take identical histories and compare them

Draw conclusions

14

Cohort studies tend to go ___ in time while case-control studies go ___.

forwards

backwards

15

Case control studies are good for studying ___ diseases.

rare

16

What statistic is associated with case control studies?

Odds ratio

17

How is an odds ratio calculated?

Odds ratio = Odds of event when exposed / Odds of event when not exposed

18

An odds ratio of < 1 means that the risk is (lower / higher) in the exposed group.

lower

19

An odds ratio of > 1 means that the risk in the exposed group is (lower / higher) than the risk in the non-exposed group.

higher

20

Can causation be proved by a case-control study?

No

histories rely on memory