Suppose a statistics teacher wants to know whether the numberof hours students spend studying in a group affects the finalcourse grade. In each part, explain whether the research methoddescribed is a randomized experiment or an observationalstudy.
a) Each student keeeps a log of the hours he or she spendsstudying in a group and reports the total after the course iscompleted.
b) Students are randomly assigned to study groups. The teachertells each group how often to meet. This varies from one hour theday before each exam to two hours per week.
c) Students voluntarily join groups based on how often thegroups will meet. The groups are designated as meeting weekly,meeting only before exam,s or meeting whenever enough members feelthat it is necessary.