Final answer:
The first method is a simple random sample because every student has an equal chance of being chosen. The second and third methods are random but not simple random because the selection of students depends on their row placement, not their individual probability.
Step-by-step explanation:
In the context of selecting a sample from a class of 30 students for a survey using different methods, the classification of each sampling method can be examined as follows:
- Simple random sampling is when every member of the population has an equal chance of being selected. In this case, it applies to the scenario where all 30 students' names are put in a basket and 12 are randomly selected. This exemplifies the principles of a simple random sample because it gives an equal probability to each student to be chosen.
- When two of the five rows are randomly selected and all students from those rows are chosen, this method is considered random but not simple random. This is because while the selection of rows is random, not every individual has an equal chance of being selected, since the outcome depends on which row they are sitting in.
- Selecting one odd row and one even row and taking all students in the chosen rows, while random in terms of row selection, also does not qualify as simple random sampling. Like the previous method, it's random but not simple random, as the individual chance for selection is unequal and contingent upon the student's row position.
Each sampling technique has its advantages and disadvantages, and the choice depends on the research objectives and practical considerations.