Statistics - bias types

Question 1

Response bias

Answer 1

Those who respond to a questionnaire or volunteer for a trial are not representative of the population

Question 2

Observer bias

Answer 2

There is observer subjectivity about the outcome

Question 3

Publication bias

Answer 3

Studies that report negative findings are less likely to be published
A symmetrical, inverted funnel shape indicates an absence of publication bias

Question 4

Recall bias

Answer 4

Patients are more likely to recall exposures that they believe are related to the outcome
particular problem in case control studies

Question 5

Selection bias

Answer 5

The study sample is not representative of the population

Question 6

Berksons bias

Answer 6

Hospital patient bias.

Question 7

Hawthorne bias

Answer 7

When a study incorrectly concludes that an intervention has led to a change in outcome when in fact it is the observation itself which has resulted in a change

Question 8

Lead-time bias

Answer 8

Occurs when two tests for a disease are compared, the new test diagnoses the disease earlier, but there is no effect on the outcome of the disease

Question 9

Procedure bias

Answer 9

Occurs when subjects in different groups receive different treatment

Question 10

Late-look bias

Answer 10

Gathering information at an inappropriate timee.g. studying a fatal disease many years later when some of the patients may have died already

Question 11

Expectation bias

Answer 11

Only a problem in non-blinded trials.
Observers may subconsciously measure or report data in a way that favours the expected study outcome.

Question 12

Work-up bias

Answer 12

In studies which compare new diagnostic tests with gold standard tests, work-up bias can be an issue.May be avoidance to order gold standard test due to invasive nature

Question 13

Language bias

Answer 13

Form of reporting bias. This can occur when studies are only considered if they are in language of the study authors