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mean life
(redirected from Mean lifetime)

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mean life

In radioactivity, the average lifetime of all the nuclei of a particular unstable atomic species. This time interval is the sum of the lifetimes of all the individual unstable nuclei in a sample, divided by the total number of unstable nuclei present. It is the reciprocal of the decay constant. For a given isotope, the mean life is always 1.443 times its half-life. For example, lead-209 decays to bismuth-209 with a half-life of 3.25 hours and a mean life of 4.69 hours.


mean life [′mēn ′līf]
(physics)
The average time during which a system, such as an atom, nucleus, or elementary particle, exists in a specified form; for a radionuclide or an excited state of an atom or nucleus, it is the reciprocal of the decay constant. Also known as average life; lifetime.


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Reichheld prefers the term net present value (NPV) to the term customer lifetime value: "Admittedly, customer NPV doesn't roll off the tongue as easily as the more common term, lifetime customer value, but that term has been used most often to mean lifetime revenue stream, as opposed to the discounted stream of profit net of acquisition investment" (1996: 224).
The distribution's mean lifetime is 75 months and its median is 73 months.
 
 
 
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