A Statistics Teacher Wants to Know How Students in Her

A statistics teacher wants to know how students in her school feel about mathematics courses. She decides to administer a
survey to a random sample of students taking a mathematics course. She has several sampling plans to choose from.
a. There are four ranks of students taking the class: freshmen, sophomores, juniors, and seniors. Randomly select 15 students
from each class rank.
b. Randomly select ten math class sections and survey every student in each of those sections.
c. Each student has a nine-digit student number. Randomly choose 60 different nine-digit numbers and survey the students
that correspond to those numbers.
d. Randomly select a number from 1 to 5. Using the class roster, start at that number, then select every fifth student from the
list after that.
-If the teacher in simply surveyed all of her students, what kind of sampling would that be?
Explain why this method is biased. Be sure to name the kind(s) of bias you describe and
link it to the variable of interest.