Lecture 8: Casuality, bias and confounding

Question 1

What is a casual inference?

Answer 1

determining the effect of a phenomenon part of a wider system

Question 2

What is the name given to what would have happened in a study if we’d done things differently?

Answer 2

counterfactual

Question 3

What is another name for an estimate of a counterfactual?

Answer 3

Control

Question 4

What term is used to describe groups of people in a study who are comparable on average?

Answer 4

exchangeable

Question 5

What is the easiest way to ensure exchangeable study groups?

Answer 5

randomisation

Question 6

What is random sampling error?

Answer 6

-The random error in our population estimate(s) that results from chance fluctuations in the profile of our sample

Question 7

Is error caused by random or non-random factors?

Answer 7

non-random

Question 8

What is bias?

Answer 8

a non-random, systematic error

Question 9

What is precision?

Answer 9

a measure of how close a series of measurements are to one another

Question 10

What is accuracy?

Answer 10

how close a measurement is to the true value

Question 11

What is confounding bias?

Answer 11

Distortion of the causal association between two variables, due to a common shared cause (a confounder)

Question 12

What is a confounder?

Answer 12

a third variable that influences an association without being measured

Question 13

What is conditioning?

Answer 13

the process of reducing confounders by examining like-for-like participants (grouping participants into exposed and non-exposed groups)

Question 14

Give 3 forms of conditioning confounders:

Answer 14

1) restriction

2) stratification

3) covariate adjustment

Question 15

Describe restriction as a form of conditioning:

Answer 15

restricting the sample to a single value of the confounder

Question 16

Describe stratification as a form of conditioning:

Answer 16

calculating category-specific effects for different levels of the confounder

Question 17

Describe covariate adjustment as a form of conditioning:

Answer 17

adjusting the cofounders in a regression of the association

Question 18

What causes selection bias?

Answer 18

a systematic difference between those selected into a study sample and those that were not selected

Question 19

Give 3 types of selection bias:

Answer 19

1) sampling bias

2) participation bias

3) attrition bias

Question 20

What is sampling bias?

Answer 20

a failure to sample evenly across the population (not generalisable)

Question 21

What is participation bias?

Answer 21

people having different preferences or opportunities to participate in research

Question 22

What is attrition bias?

Answer 22

a loss of participants from the study which may be unbalanced by the exposure

Question 23

What causes information bias?

Answer 23

a systematic error in reporting, measurement or the recording of error

Question 24

Give 3 types of information bias:

Answer 24

1) response bias

2) recall bias

3) measurement bias

Question 25

What is response bias?

Answer 25

people responding in inaccurate or untruthful ways by wanting to give the right answer or downplaying undesirable traits

Question 26

What is recall bias?

Answer 26

people having different abilities to remember past information

Question 27

What is measurement bias?

Answer 27

a measurement that under or over reports systematically

Question 28

What causes experimenter bias?

Answer 28

the behaviours and actions of the experimenter whether conscious or unconscious

Question 29

Give two types of experimenter bias:

Answer 29

1) confirmation bias

2) results bias

Question 30

What is confirmation bias?

Answer 30

where findings we expect are more likely to be accepted and those that aren’t are refuted

Question 31

What is results bias?

Answer 31

being more likely to chase positive associations, seek novel results or publish positive results