For any number k greater than 1, at least (1-1/k2) of the data values lie within k standard deviation s of the mean
CHEBYSHEV'S THEOREM
Meaning of CHEBYSHEV'S THEOREM in English
Sean Woo's Finance, GIS and real estate English glossary. Английский глоссарий по ГИС(Географическая информационная система) и недвижимости Sean Woo's Finance. 2012