Which of the following scenarios contain nonbiased samples? Select all that apply. Select all that apply: Christine wants to estimate the mean grade point average of students at her school. She collects data by recording the grade point average of every 25 th student on the list of students after a randomly selected first student. Homer wants to estimate the ethnic background distribution of residents of his town. He collects data from 1000 randomly selected town residents by using a random number generator. To estimate the mean height of students at her grade school, Tammy collects data by selecting a random group of students within her classroom. To estimate the mean salary of professors at his university, Peter collects data by recording the salaries of all professors included in 12 randomly selected departments