Population is the entire aggregation of  cases that meet the designated set of criteria. It  includes a complete set of persons or objects that possess same characteristics that is of interest to the researcher. The population usually is described as Target population which  is  also called the universe, is composed of entire group of people or objects to which  the researcher w~shes  to generalize the  findings of a  study,  target population consists of people  or  things that meet the designated set of criteria of  interest to  researcher. Population is not restricted  to  human  subjects. A population might  consist of all the hospital records on  file or all blood  samples. The researcher usually  samples from an available group,  calledqthe  accessible population or  study population. The researcher needs to identify the accessible population from which generalization of  the study finding  can be  drawn. The conclusions of  research study are based on  data obtained from accessible population and the statistical inferences should 60  be made only to  the group from which sample was randomly selected.