Which of the following is a major weakness of a volunteer sample?

The major weakness of a volunteer sample is that it can be expensive and take more effort. Volunteer samples often rely on individuals who are willing to participate actively, which can lead to a less diverse group of participants. This can limit the generalizability of the findings, as those who volunteer may have specific characteristics or motivations that differ significantly from those of the broader population.

Additionally, while obtaining a volunteer sample might seem straightforward, researchers may face difficulties in recruiting sufficient participants or may need to invest significant resources in ensuring a diverse representation. This process can involve extensive outreach, marketing, and sometimes compensation incentives to encourage participation, which can be costly and time-consuming.

In contrast, a volunteer sample generally lacks the high representativeness mentioned in one choice, tends not to inherently offer better ecological validity, and does not usually involve compensated participants. Therefore, the correct understanding centers on the complexities and resources involved in obtaining a suitable volunteer sample rather than the advantages that may arise from other sampling methods.