Epidemiology

Question 1

What is the gold standard for drug testing?

Answer 1

Controlled clinical trial

Question 2

What is equipoise?

Answer 2

A state of genuine uncertainty about the benefits/harms resulting from a regimen.

Question 3

Equipoise calls for what?

Answer 3

Randomized controlled trial

Question 4

What is the difference between the experimental population and the study population?

Answer 4

Experimental population is the group you chose before applying excluding criteria

Question 5

Why is randomization important? What bias does it diminishes?

Answer 5

Prevents selection bias

Minimizes confounding

Question 6

Why is concealment of allocation (the fact that the physician does not know who is a control or on trial during a study) important?

Answer 6

Prevents missclassification of exposure status

Prevents missclassification of outcome status

Question 7

What is the Hawthorne effect?

Answer 7

People in the control group (and know they are in the control group) that change the behaviour to help the study

Question 8

What are the limitations of randomized control trial?

Answer 8

Doesn’t represent routine practice
Not effective to study uncommon but serious adverse effects
Expensive and time consuming
Sometimes unfeasible for ethical concerns

Question 9

What is the Power of study?

Answer 9

Probability that there’s an association and that the study shows it

Question 10

What is the formula for Power?

Answer 10

1 - (percentage of type II errors)

Question 11

At which percentage is the Power usually fixed?

Answer 11

80%

Question 12

What can increase the Power of a study?

Answer 12

A larger sample population

Question 13

What is the Number Needed to Treat (NNT)?

Answer 13

The NNT is the average number of patients who need to be treated to prevent one additional bad outcome (e.g. the number of patients that need to be treated for one of them to benefit compared with a control in a clinical trial)

Question 14

Number Needed to Treat (NNT) is the inverse of what?

Answer 14

Absolute Risk Reduction (ARR)

Question 15

What is the formula for Absolute Risk Reduction?

Answer 15

Control group event rate - Experimental group event rate

Question 16

What is the formula for Number Needed to treat?

Answer 16

1
______
(Control group event rate - Experimental group event rate)

Question 17

What is sampling variation?

Answer 17

Uncertainty caused by the fact that individuals differ in their response to treatment

Question 18

What is the Null hypothesis

Answer 18

Supposing there is no difference between control and trial groups

Question 19

Do we reject the null hypothesis if the p value is < 0.05?

Answer 19

We reject the null hypothesis

Question 20

Do we reject the null hypothesis if the p value is > 0.05?

Answer 20

We keep the null hypothesis; the results are statistically insignificant

Question 21

3 factors influencing the p-values

Answer 21

Magnitude of the treatment effect
Sample size
Standard deviation of the data

Question 22

What is Type I error?

Answer 22

Saying there’s a difference (an association between two phenomenas) between two groups, but there’s none

Question 23

What is Type II error?

Answer 23

Saying there’s no difference (no association between two phenomenas) between two groups, but there is

Question 24

What is the arbitrary level of confidence?

Answer 24

95%

Question 25

How do you calculate confidence intervals?

Answer 25

Effect size ± (1.96 x measure of variation)

Question 26

What distinguishes meta-analyses from systematic reviews?

Answer 26

Meta-analyses are quantitative and systematic reviews are qualitative

Question 27

Which is higher evidence, meta-analyse or systematic review?

Answer 27

Meta-analyse

Question 28

Which is higher evidence, traditional meta-analyse or individual patient data meta-analyse?

Answer 28

Individual patient data meta-analyse

Question 29

Characteristics of traditional narrative reviews?

Answer 29

Written by an expert in the field Informal/subjective methods to collect and interpret info (systematic reviews follow a predetermined and explicit method)

Question 30

What is a "pooled analysis"

Answer 30

An individual patient data meta-analyse

Question 31

What is quality assessment?

Answer 31

Having the data studied synthesized

Question 32

What is the defining characteristic of fixed-effects models in statistical analyses?

Answer 32

They assume no between-study heterogeneity

Question 33

What is the defining characteristic of random-effects models in statistical analyses?

Answer 33

They assume heterogeneity within- and between studies (due to difference in studied populations and study designs)

Question 34

What is I^2 statistics?

Answer 34

A method to estimate the proportion of the total heterogeneity that is due to between-studies heterogeneity

Question 35

When can a meta-analysis mislead (4)?

Answer 35

When a meta-analysis is done outside of a systematic review When poor quality studies are included (and good ones excluded) When no attention is given to heterogeneity When there's presence of biases

Question 36

What is the publication bias?

Answer 36

Studies finding positive correlation between phenomena tend to get more published