Simple random sampling selects units out of a population such that each popu unit has an equal chance of being drawn. The units in the population are assigned numbers from l to N, and numbers between 1 and N are drawn from a ran- dom number table or from a computer program especially designed to produce such numbers. The specific units in the population that correspond to these random num bers become the randomly drawn sample Sequential sampling d a ample from every nth element in the population This procedure is based on the assumption that the target population has been listed random orde