Answer:
If Ken wants to compare how many hours a week sixth graders spend doing mathematics homework to how many hours a week that eleventh graders spend doing mathematics homework and randomly selects ten sixth graders and ten eleventh graders and records how many hours each student spent on mathematics homework in a certain week then this is an observational study.
Step-by-step explanation:
An observational study depends on the data set statistical analysis, researchers do not manipulate any variable to reach conclusions. They design question-measurement to collect information without trying to affect their answers.
A survey is part of an observational study assessed on a sample population through controlled sample questions to collect specific data asking determined people and the response variable is the number of correct answers collected which are not influenced either.
In a controlled experiment, the researcher manipulates the sample population grouping people to assign them with some treatment or to do an specific task. Different groups are formed and assigned with different tasks to get the information wanted or to know proportion of the population in certain task.
