'A good sample is generally based on correctness and continuity’

'A good sample is generally based on correctness and continuity’. In the context of above statement explain the characteristics of good sample.

The characteristics of goods sample are
(i) The sample should be independent.
(ii) All individual units included in the sample should be Independent.
(iii) The reliability of sample should be based on correctness.
(iv) The sample should be based on continuity and law of inertia of large numbers.