You're interested in whether tutoring is more effective when the student volunteers to be tutored. You compare the test scores of two groups of students: those who

chose to go to after-school tutoring sessions and those who are required to go to the

sessions by the school administration. This is an example of a (an):

Observational Study

Step-by-step explanation:

The process where a researcher observe or study a group of people or an individual for the sole aim of achieving a result by comparing the test results or outcome of study is called OBSERVATIONAL STUDY just as the information given in which two groups of students where observe for the sole aim of knowing whether to tutor is more effective or not in a situation where the students volunteer them self to be tutored by comparing the outcome of the study carried on the students.

Therefore This is an example of a (an):OBSERVATIONAL STUDY

it would be 6xy and -16xy.

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