Week 122 - Measurements in population I Flashcards Preview

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Flashcards in Week 122 - Measurements in population I Deck (36):
1

What is incidence?

Proportion of a group that will develop a certain disease over a time period

2

What is prevalence?

Amount/proportion of people that have a disease at a given time

3

List the study order of hierachy of evidence?

1) Systematic reviews with at least one RCT

2) RCT

3) Non RCTs

4) Cohort studies

5) Case-control studies

6) Self controlled case series

7) Ecological studies

8) Cross sectional studies of incidence and prevalence

9) Case series and case reports

4

What is an RCT?

A randomised controlled trial

Randomisation of sorting people into groups removes any confounding factors between the intervention group and control group

5

What is a self controlled case series?

A study in which the incidence of a certain outcome is compared to the incidence of the outcome when the individual is not exposed

e.g. occurence of adverse reaction when given a drug compared to when not given

6

What is a cross sectional study?

A study that collects data on incidence/prevalence of a disease in a population at a specific point in time

7

What is an ecological study?

A study in which populations/groups are analysed to study effects of risk factor on health

e.g. rates of obesity in different countries

8

What is the disadvantage of an ecological study?

Hard to control due to confounding variables

9

What is a case report study?

A detailed report of a patient with a condition of interest

10

What is a case series study?

A descriptive study of patients with a known exposure or condition

11

What is a disadvantage of case-series study?

Can involve selection bias

12

List the two types of research studies?

Experimental studies

Observational studies

13

What is an experimental study?

Study which exposure is determined as part of study design

14

What is an observational study?

Study in which exposure is not determined as part of the study design

- already existing expossure and consequences are studied

15

Give an example of an experimental study?

RCTs

Non-randomised trials

16

What is the null hypothesis?

Statement being tested in a test of hypothesis

17

What is the alternative hypothesis?

What is believed to be true if the null hypothesis is false

18

What is a case control study?

A study which starts with the identification of people:
- with the disease of interest, and a
- control group without the disease

19

What is a retrospective case control study?

A case control study which starts with the case and looks back at exposure to see if there is an associated risk

20

What is a prospective case control study?

A case control study which recruit individuals as they develop the disease of interest

21

What is a p-value?

Probability of observing a difference as large as previously seen in a study due to chance

p-value < 0.05 => statistically significant

22

What is a cohort study?

A study that starts by looking at a certain group of people and identifies those who are exposed to the risk factors and those who are not.

It then compares the incidence of disease development between the two exposure groups.

23

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

Prospective = current exposure

Retrospective = identifies "past" exposure to risk factors

24

What are the advantages of a case control study?

Better for rare diseases

Retrospective case controls are quick and cheap

25

What are the disadvantages of a case control study?

Prone to bias

Time of first exposure to risk factor is difficult to judge

Incidence can't be determined

26

What are the advantages of a cohort study?

Better for rare exposures

View the multiple effects of one exposure

Less prone to bias

Incidence can be determined

27

What are the disadvantages of a cohort study?

Can be slow and expensive

28

What are the two types of random errors?

Type 1 = alpha error

Type 2 = beta error

29

What is a type 1 error?

A false positive

30

What is a type 2 error?

A false negative

31

How can type 1 errors be controlled?

By lowering the statistical significance level

32

How can type 2 errors be controlled?

Increase sample size and power of the study

33

What is sensitivity?

Measurement of how good a test is at diagnosing disease?
i.e. true positive rate

A high sensitivity reduced type 2 error

34

What is specificity?

Measurement of how good a test is at diagnosing no disease?
i.e. true negative rate

High specificity reduces type 1 errors

35

What is the formula for relative risk?

(Absolute risk when exposed) / (absolute risk when non-exposed)

i.e. [De / (De + He)] / [De' / (De' + He')]

36

What is the formula for odds ratio?

Odds of exposed / Odds of non-exposed

i.e. (De / He) / (De' / He') = (De He') / (He De')