Subset, strict subset, and superset  Probability and Statistics  Khan Academy  Summary and Q&A
TL;DR
This video explains the concepts of sets, subsets, and supersets, illustrating with examples and providing notations for each.
Questions & Answers
Q: What is a subset?
A subset is a set where every element is also a member of another set. In other words, all the elements in the subset are also present in the larger set.
Q: Is set B a subset of set A?
Yes, set B is a subset of set A. Every member of set B (1, 7, and 18) is also present in set A.
Q: Can set C be considered a subset of set A?
No, set C is not a subset of set A. While set C does have elements that are present in set A (18, 7, and 1), it also contains an additional element (19) that is not present in set A.
Q: What is a strict subset?
A strict or proper subset refers to a subset that is not equal to the larger set. In the video, it is denoted by crossing out the equal part of the less than or equal sign. Set B is a strict subset of set A because it contains elements from A but not all the elements of A.
Summary & Key Takeaways

The video introduces sets A, B, and C, consisting of different numbers.

A subset is a set where every element is also a member of another set.

Set B is a subset of set A, but not equal to A, making it a strict or proper subset.