Q.A __________ is one where each item in the universe has an equal chance of known opportunity of being selected.

A sample is a subset of the population selected for study in place of a full census. The commonly used probability sampling methods are:

• Simple Random Sampling (SRS): every unit has an equal, independent chance of selection (lottery or random numbers).
• Stratified Sampling: the population is divided into homogeneous strata, and a sample is drawn from every stratum, usually in proportion to its size — ensures every distinct sub-group is represented.
• Systematic Sampling: units are selected at a fixed interval $k = N/n$ from an ordered list, after a random start. …