Which of the following is an example of stratified sampling when obtaining a sample of 100 high school students? A. Choosing 100 students at random from a specific grade level at a high school.B. Choosing 100 students sitting in one random section of the cafeteria at a high school.C. Choosing 25 students at random from each of four different grade levels at a high school.D. Choosing 100 students at random from a high school. E. Choosing 100 students at random from an AP Statistics class at a high school.

Option C - Choosing 25 students at random from each of four different grade levels at a high school

Step-by-step explanation:

For us to achieve the conditions for a stratified random sample, the target population must be split into different groups which in this case, it's grade levels.

Looking at the 5 options given in the question, Options A, B, D and E are random but they are not truly stratified in their sampling approach. This is because the sample population must be selected at random from each of these groups and it's only option C which is choosing 25 students from each of four different grade levels or groups that reflects that.

Step-by-step explanation:

90-2x + 3x + 60 = 180

90 + x + 60 = 180

x + 150 = 180

x = 30°