Many Americans Complain About Being Sleep Deprived $\mu$ _C = Mean Sleep Time for the Control Group

Many Americans complain about being sleep deprived. A team of psychologists researched the reasons for this sleep deprivation. After determining that one reason was poor time management, they devised a program to help people manage their time better. They recruited a random sample of 30 people at a major shopping center and randomly split them into three groups of size 10. Group 1 (the controls) received a logbook asking them to record the number of hours slept for a week but nothing else. Group 2 (the informed group) was shown a video to help improve time management. Group 3 (the intervention) participated in a two-day training course on improving time management. Groups 2 and 3 were also asked to keep records for one week on the number of hours slept. The psychologists were interested in learning if providing information or an intervention affects sleep time. The null hypothesis the psychologists wished to test-where $\mu$ _C = mean sleep time for the control group, $\mu$ _IG = mean sleep time for the information group, and $\mu$ _IV = mean sleep time for the intervention group-is given by:

A) H₀: $\mu$ _C = $\mu$ _IG and $\mu$ _IG= $\mu$ _IV.
B) H₀: $\mu$ _C = $\mu$ _IG= $\mu$ _IV.
C) H₀: $\mu$ _C = $\mu$ _IG or $\mu$ _IG = $\mu$ _IV.
D) H₀: at least of $\mu$ _C = $\mu$ _IG or $\mu$ _IG = $\mu$ _IV holds.