Final answer:
A voluntary response sample may introduce sampling bias in statistical methods because it can be unrepresentative of the population. This is due to the self-selection of participants, leading to skewed results not reflective of the entire population.
Step-by-step explanation:
A voluntary response sample is generally unsuitable for methods of statistics because it may introduce sampling bias. When individuals are allowed to volunteer for a sample, there is a likelihood that those who choose to participate have certain characteristics or opinions that differ from the general population. This can lead to results that do not accurately reflect the characteristics of the entire population. In contrast, random sampling ensures that every member of a population has the same chance of being included in the study, thereby reducing potential biases and making the sample more representative of the population.
For example, if a survey on a controversial topic relies on volunteers, those who feel strongly about the subject are more likely to participate, skewing the results. This is why choosing a random sample is an effective method, as highlighted in option D of the provided choices, where 'Everyone has the same chance of being part of the study' ensures a more representative and unbiased sample.