Efficacy

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Efficacy is the ability to produce a desired amount of a desired effect.

1 Explanation
2 See also

[edit] Explanation

[edit] Medical

In a medical context it indicates that the therapeutic effect of a given intervention (e.g. intake of a medicine, an operation, or a public health measure) is acceptable. 'Acceptable' in that context refers to a consensus that it is at least as good as other available interventions to which it will have ideally been compared to in a clinical trial. For example, an efficacious vaccine has the ability to prevent or cure a specific illness in an acceptable proportion of exposed individuals. In strict epidemiological language, 'efficacy' refers to the impact of an intervention in a clinical trial, differing from 'effectiveness' which refers to the impact in real world situations.

The concept of 'self-efficacy' is an important one in the self-management of chronic diseases because doctors and patients often do not follow best practice in using a treatment. For instance, a patient using combined oral contraceptive pills to prevent pregnancy may sometimes forget to take a pill at the prescribed time; thus, while the perfect-use failure rate for this form of contraception in the first year of use is just 0.3%, the typical-use failure rate is 8%.[1]

[edit] Pharmacology

In Pharmacology, efficacy refers to the ability of a drug to induce a certain action at a certain concentration. This must be distinguished from the affinity, which refers to the ability of the drug to bind to its receptor at a certain concentration.

[edit] Lighting

In lighting design, "efficacy" refers to the amount of illumination produced by a lamp (a light bulb or other light source), usually measured in lumens, as a ratio of the amount of energy consumed to produce the illumination, usually measured in watts. This is not to be confused with efficiency which is always a dimensionless ratio of output divided by input which for lighting relates to the watts of visible energy as a ratio of the energy consumed in watts. The visible energy can be approximated by the area under the Plancks curve between 300 Nm and 700 Nm for a blackbody at the temperature of the filament as a ratio of the total energy under the blackbody curve. Efficiency values for light from a heat source are typically less than two percent.

[edit] Difference Amplifiers

The efficacy of a differential amplifier is measured by the degree of its rejection of common-mode signals inpreference to differential signals. Refer to common-mode rejection ratio (CMRR).