bias

Question 1

lead time bias

Answer 1

occurs when two tests for a disease are compared

new test diagnoses the disease earlier but no effect on outcome

Question 2

procedural bias

Answer 2

subjects in 2 different groups receive different treatment

Question 3

late look bias

Answer 3

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

Question 4

Hawthorne effect

Answer 4

Describes a group changing it’s behaviour due to the knowledge that it is being studied

Question 5

Expectation bias (Pygmalion effect)

Answer 5

. Observers may subconsciously measure or report data in a way that favours the expected study outcome.

Question 6

Work-up bias (verification bias)

Answer 6

Sometimes clinicians may be reluctant to order the gold standard test unless the new test is positive, as the gold standard test may be invasive (e.g. tissue biopsy).

Question 7

Publication bias

Answer 7

Failure to publish results from valid studies, often as they showed a negative or uninteresting result.

Question 8

Recall bias

Answer 8

Difference in the accuracy of the recollections retrieved by study participants, possibly due to whether they have disorder or not. E.g. a patient with lung cancer may search their memories more thoroughly for a history of asbestos exposure than someone in the control group.

Question 9

sampling bias

Answer 9

subjects are not representative of the population

Question 10

non-responder bias

Answer 10

. If a survey on dietary habits was sent out in the post to random households it is likely that the people who didn’t respond would have poorer diets than those who did.