Here, by default both apt-cache and aptitude search for a package on whole list of packages in repository, but output of aptitude shows whether the package is installed on the system or not by giving a per-package flag which here is 'p' indicating that package is present but not installed and 'i' which indicates that the package is installed, whereas apt-cache just lists the package and its one-line detail without telling if package is installed or not.
deviation deÂ·viÂ·aÂ·tion (dÄ'vÄ-Ä'shÉn) n. A turning away or aside from a normal course. An abnormality. Deviant behavior or attitudes. The difference, especially the absolute difference, between one number in a set and the mean of the set.
Quartile Deviation (Q. D.) is half of the difference between the first and third quartiles. Hence, it is called Semi Inter Quartile Range. In Symbols, Q. D = Q3 â Q1. Among the quartiles Q1, Q2 and Q3, the range Q3 Q1 is called inter quartile range and (Q3-Q1)/2, Semi inter-quartile range.