The Parent Teacher Organizations (PTOs) at all ten high schools in a large school district decided to sponsor a study of students’ social media use. Random samples of students were drawn from each school. Table 7.3 shows the proportion of students who have ever taken a complete break from social media for longer than one month for the ten high schools.

a. Assume that social media behavior across these schools is actually very similar. Explain how knowledge of sampling explains why we still observe sample differences across schools in the percentages of students who have taken a break from social media.

b. What is the mean of proportions for the ten high schools?

c. Is the mean that you calculated for Part b equal to the proportion of all students in the district’s high schools who have taken a social media break?