JAMAevidence Glossary

Terms are derived from Users' Guides to the Medical Literature: A Manual for Evidence-Based Practice, 2nd Edition and The Rational Clinical Examination: Evidence-Based Clinical Diagnosis. Updated December 2009.
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Face validity
The extent to which a measurement instrument appears to measure what it is intended to measure.

Fail-safe N
The minimum number of undetected studies with negative results that would be needed to change the conclusions of a meta-analysis. A small fail-safe N suggests that the conclusion of the meta-analysis may be susceptible to publication bias.

False negative
Those who have the target disorder but the test incorrectly identifies them as not having it.

False positive
Those who do not have the target disorder, but the test incorrectly identifies them as having it.

Feedback effect
1. The impact of performance evaluations on clinicians’ behavior. 2. The improvement seen in medical decision because of performance evaluation and feedback.

Feeling thermometer
A feeling thermometer is a visual analogue scale presented as a thermometer, typically with markings from 0 to 100, with 0 representing death and 100 full health. Respondents use the thermometer to indicate their utility rating of their health state or of a hypothetical health state.

Fixed-effects models
A model to generate a summary estimate of the magnitude of effect in a meta-analysis that restricts inferences to the set of studies included in the metaanalysis and assumes that a single true value underlies all of the primary study results. The assumption is that if all studies were infinitely large, they would yield identical estimates of effect; thus, observed estimates of effect differ from one another only because of random error. This model takes only within-study variation into account and not between-study variation.

Flick sign
When asking the patient, "What do you actually do with your hand(s) when the symptoms are at their worst?" the patient demonstrates a flicking movement of the wrist and hand, similar to that used in shaking down a thermometer.

Focus group
A small group of individuals (typically gatherings of four to eight people with similar background or experience) who meet together and are asked questions by a moderator about a given topic.

Follow-up
The extent to which investigators are aware of the outcome in every patient who participated in a study.

Follow-up (complete)
The investigators are aware of the outcome in every patient who participated in a study.

Foreground questions
These clinical questions are more commonly asked by seasoned clinicians. They are questions asked when browsing the literature (eg, what important new information should I know to optimally treat my patients?) or when problem solving (eg, defining specific questions raised in caring for patients, and then consulting the literature to resolve these problems).

Funnel plot
A graphic technique for assessing the possibility of publication bias in a systematic review. The effect measure is typically plotted on the horizontal axis and a measure of the random error associated with each study on the vertical axis. In the absence of publication bias, because of sampling variability, the graph should have the shape of a funnel. If there is bias against the publication of null results or results showing an adverse effect of the intervention, one quadrant of the funnel plot will be partially or completely missing.