The main feature of the sample that determines its quality is (choose the correct answer): the representativeness of the population the conformity of the sample distribution to the normal form the systematic nature of the selection the validity and reliability of the measurement

The correct answer is: the validity and reliability of the measurement.<br /><br />The main feature of a sample that determines its quality is the validity and reliability of the measurement. This means that the sample should accurately represent the population and the measurements taken should be consistent and free from errors. The representativeness of the population, conformity of the sample distribution to the normal form, and systematic nature of the selection are important factors, but they do not directly determine the quality of the sample.