bob wants to see if drinking caffeine in your water can keep you awake longer. he finds 60 volunteers for his study. he fills 120 stainless steel bottles with water. in half the bottles he places 48 milligrams of caffeine (about as much as in a diet coke). you cannot taste the caffeine. he randomly assigns 10 students to drink 1 bottle of regular water at 8pm; 10 students to drink 1 bottle of caffeinated water at 8pm; 10 students to drink 2 bottles of regular water at 8 and 9 pm; 10 students to drink 2 bottles of caffeinated water at 8 and 9 pm; 10 students to drink 3 bottles of regular water at 8pm, 9pm, and 10pm; and 10 students to drink 3 bottles of caffeinated water at 8, 9, and 10 pm. no one knows which subject got which treatment. he watches the volunteers and records the times that they fall asleep and compares the sleep times for all the groups. stat 1430 recitation 2a experiments
20. what is the independent variable in this study? be careful. 21. how many treatment groups are there (count the control groups in this.)
22. what is the response variable?
23. make a drawing that shows how you can randomly assign the 60 people to the different treatments. tell who is in in which treatment. your method must be truly random. (hint: can statcrunch help you generate random numbers? and see!)
24. evaluate this experiment in terms of the 3 criteria listed in your lecture notes: (list the criteria first, then give your opinion.) one: two: three:
25. list at least one confounding variable in this study.
26. suggest an improvement for this study.