According to the concepts of population, individual and sample size.
The group refers to the whole of the inspected object, and the individual is the inspected object in the group. A sample is a part of individuals extracted from the population, and the sample size refers to the number of individuals in the sample. When we distinguish the four concepts of population, individual, sample and sample size, we must first make clear the object to be investigated, so as to make clear the population and individual. Then we find out the samples according to this part of the collected data, and finally determine the sample size according to the samples.
Solution: The object of this question is the time for seventh-grade students to do their math homework on weekends, so it is generally the time for seventh-grade students to do their math homework on weekends;
Individual is the time that every seventh-grade student spends on math homework on weekends;
The sample is 100, so the sample size is 100.