I already tried choosing options 2345 and 3456 but both were

I already tried choosing options 2,3,4,5 and 3,4,5,6 but both were wrong. I have to guess all of them correctly to get credit. And if you could please explain why you choose the ones you do thatd be great! Thanks in advance

Suppose a statistics instructor wants to determine if group study session are beneficial to students, and if so whether or not the amount of time spent in group study makes a difference. Which of the following scenarios below refer to unbiased controlled experiments that the instructor could run? For all of these scenarios, assume that the instructor is keeping track of the grades of all students in the class. Select all that apply. You have three tries, and you must pick only the correct scenarios for credit. Each student in the class keeps a log of the hours he/she spends studying in a group. Students report the total number of study hours after the course is completed O The instructor puts all of the freshmen in the class into one group, all of the sophomores into another, all of the juniors into another, and finally all of the seniors into another. The instructor then randomly picks a certain number of hours for each group to study per week. O Students are randomly assigned to four groups. Each group votes on how much studying they will do, and then studies that amount each week. Students are randomly assigned to two groups. One is told to only study on an individual basis, while the other is told to participate in group study sessions. O Students are randomly assigned to four study groups. The instructor assigns a different number of study hours to each group. Four groups are set up. Students in the first group are told not to study at all. Students in the second group are told to study on an individual basis. Students in the 3rd group are told to study 2 hours per week. Students in the 4th group are told to study 4 hours per week. Students then choose which group they want to be in

Solution

We are trying to perform an unbiased and controlled experiment.

For an unbiased experiment, the sample has to be randoly chosen. Since the experiment has to be controlled as well as it is to be determined whether there is impact of the hours of study in the grades, we need to divide the groups into 3 distinctions at least.

- Individual studies

- Group study for a certain hours

- Group study for a longer duration.

So, the best option that fits into this description is option 6.

Option 4 will not help in studying if the number of hours make any difference and option 1,2 and 5 will not help in distinguishing between individual and group studies.

Option 3 does not have a controlled variable as the number of hours is determined by the students and not the experimenter.

Note: IF comparison between individual and group study is not absolutely necessary, 1.2 and 5 may also be considered as right answers.