A survey is to be taken to ascertian student opinions about the quality of teaching at a high school. Below are some possible methods for picking 100 students out of the 2000 students registered at the school. For each, indicate what kind of sampling strategy is used.
a) Using an official school roster of the 2000 students, pick every 20th name.
b) sparate the students by class ( freshman, sophomore, junior, senior). pick a simple random sample of size 25 from each of the four groups, and then combine these students into one sample of size 100.
c) Using a random number table, 100 names are chosen from the list of 2000 students registered at high school
d) Separate the students by home-room assigned ( each home-room has 25 students). Pick a random sample of four home-rooms. If a home-room is selected, all students in that home-room are included in the sample.