Astudy conducted by researchers from the department of education wanted to know the average debt of college students in the united states. in order to obtain a sample representative of all students, the researchers divided college students into the four classes (freshman, sophomore, junior, and senior) and then took a random sample of students from each class. which sampling method did they use?
a) stratified random sampling
b) systematic random sampling
c) cluster sampling
d) simple random sampling

A) Stratified random sampling

Step-by-step explanation:

Since , the researchers divided college students into the four classes (freshman, sophomore, junior, and senior) and then took a random sample of students from each class.

That means each category is participating in the sample.

It means , they used stratified sampling method where each class denotes a strata.

Here ,  each category participates in researcher's analysis.

Hence, the correct answer is A) Stratified random sampling .

in simplified version   it would be x ≤-4

step-by-step explanation:

multiply each term in x ≤-4 by -1