In a study of attitudes to university policies, a researcher chose initially 150 first-year students, 130 second-year students and 100 third-year students (N1=380).

In a study of attitudes to university policies, a researcher chose initially 150 first-year students, 130 second-year students and 100 third-year students (N1=380). Then, the researcher chose 25 male and 25 female students from each year group who were finally interviewed (N2=150). The sampling procedure used in this study was

Probability sampling

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Stratified sampling

Maximum variation sampling