Calculated free size differs from system stats

Calculated free size differs from system stats

References

Reference NO 1

http://stackoverflow.com/questions/15202923/calculated-free-size-differs-from-system-stats

Reference NO 2

http://en.wikipedia.org/wiki/Effect_size

Reference NO 3

http://en.wikipedia.org/wiki/Margin_of_error

Reference NO 4

https://www.zabbix.com/documentation/1.8/manual/config/items

Reference NO 5

http://www.epibiostat.ucsf.edu/biostat/sampsize.html?iframe=tr

Reference NO 6

http://php.net/manual/en/function.disk-free-space.php

Reference NO 7

http://docs.oracle.com/cd/B19306_01/server.102/b14211/memory.htm

Reference NO 8

http://statpages.org/javasta2.html