Samples and uncertainty
The idea
A sample is a subset of a population. Its selection affects what conclusions can be drawn. A large biased sample can still misrepresent the population. Describe who could respond, who actually responded, and what uncertainty or missing groups remain.
Worked example
Surveying only a chess club about favorite activities cannot establish the preferences of the entire school. A more representative selection would include students from different groups.
Another application
An online survey announced only during one club meeting may miss most students. Offering access across different classes or using an appropriate sampling plan can improve coverage; the details still need review.
A common misunderstanding
A sample can omit important groups even when many people respond. Describe who had a realistic opportunity to participate.
Try it yourself
Design a school survey. Define the population and selection method. Identify one group your method might miss and how to improve coverage.
Check your understanding
Does a large sample automatically eliminate selection bias?
Reveal the explained answer
No. How participants are selected still matters.