Question

what is required for an independent random sample

Answer 1

For selecting independent random sample the first criteria is that the probability of selection of any individual sample is independent of other or in other words we may say that the chance of selecting any one of sampling unit is equal.i.e. if first individual sample is selected then the remaining have equal chances of being selected.

In case of with and without replacement too one can draw a random sample.for example - a bag containing 4,5 and 6 green,white and red ball respectively. if we draw a red ball with replacement then in this case we easily draw a random sample as the probability of each selection of red ball is same.

If we select a red ball without replacement then one can select another red ball after first red ball has been with equal chances of drawing red ball out of remaining 5 red ,4 green and 5 white balls.so in without replacement case one can also draw random sample.