Stats

Question 1

Define Incidence

Answer 1

Number of new cases of disease per year

Question 2

Define prevalence

Answer 2

Overall proportion of population with disease

Question 3

Define bias

Answer 3

Anything that statistically influences the conclusions about a group and distorts comparisons

Question 4

What is Berkson bias

Answer 4

Arises when study includes hospitalised patients. These patients may have exposure to risk factors than are significantly greater than the population at large which can disrupt association between exposure and outcome

Question 5

What is allocation bias

Answer 5

Systematic difference in how participants are assigned to groups

Question 6

What is apprehension bias

Answer 6

When a study participant behaviours differently due to being observed

Question 7

What is ascertainment bias

Answer 7

• When data for a study are collected such that some members are less likely to be in the final result than others

Question 8

What is attrition bias

Answer 8

When individuals drop out of groups unequally

Question 9

What is availability bias

Answer 9

Researchers use information that is readily available rather than collecting all

Question 10

What is chronological bias

Answer 10

Participants recruited at different time points may vary in exposure

Question 11

What is compliance bias

Answer 11

Participants that comply with an intervention differ in someway from those who don’t

Question 12

What is data dredging

Answer 12

Occurs when multiple sub-group analyses are performed on the same data. Increases probability of type 1 error

Question 13

What is the Hawthorne effect

Answer 13

Individuals modify an aspect of their behaviour in response to their awareness of being observed

Question 14

Hot Stuff Bias

Answer 14

When a topic is fashionable investigators may be less critical in their approach and editors want to publish

Question 15

Hypothetical bias

Answer 15

When individuals stated behaviour differs to their real behaviour

Question 16

Industry sponsorship bias

Answer 16

When methods and results of a study support interests of funding organisation

Question 17

Information bias

Answer 17

Bias that occurs due to systematic differences in collection, recording or handling of information used in a study

Question 18

Observer bias

Answer 18

Systematic difference between value observed - due to observer variation, and the true value

Question 19

Performance bias

Answer 19

Systematic differences in the care provided to members of different study groups

Question 20

Popularity bias

Answer 20

Difference in uptake of healthcare as a result of public interest in a disease or condition - this leads to a selection bias

Question 21

Publication Bias

Answer 21

Likelihood of study being published affect findings of the study

Question 22

Neyman bias

Answer 22

Also known as prevalence-incidence bias.

Excluding patients with severe forms of the disease - will make disease appear less severe.

Excluding patients who have recovered - will make the disease seem more severe.

Greater time between exposure and investigation increases this risk. More common in long-acting conditions.

Case-control studies are most susceptible.

Question 23

Recall bias

Answer 23

Systematic error due to differences in accuracy of recall of past events

Question 24

Selection bias

Answer 24

Occurs when individuals in a group or study differ systematically from the population at interest

Question 25

Unacceptability

Answer 25

Systematic difference in response rates or uptake of tests due to their unacceptability. (eg. measurements that hurt or embarass may be refused)

Question 26

Volunteer bias

Answer 26

Participants volunteering to take part in the study have intrinsically different characteristics to population of interest