Which of the following is NOT necessarily a characteristic of a SRS? Each individual unit has an equal chance of being selected. All subgroups of a population will be equally represented in the sample. Each possible sample has an equal chance of being selected.

The correct answer is: All subgroups of a population will be equally represented in the sample.<br /><br />Explanation: In a Simple Random Sample (SRS), each individual unit has an equal chance of being selected, and each possible sample has an equal chance of being selected. However, it is not necessarily true that all subgroups of a population will be equally represented in the sample. The representation of subgroups in the sample depends on the distribution of the population and the random selection process.