In a study comparing two treatments for a whiplash injury, one group of patients received the usual emergency department care (normal consultation plus an advice leaflet) and the other group received...

In a study comparing two treatments for a whiplash injury, one group of patients received the usual emergency department care (normal consultation plus an advice leaflet) and the other group received “active management” care (normal consultation plus additional help). Twelve months after the initial contact, the patients were asked to rate the benefits they felt from their treatment. The results are shown in Figure 2.6 for each group (the group with missing values has been omitted). What percentage of patients felt “Much better” in each group? What percentage felt “Much worse”? How do you think that the missing values might affect the reliability of results in general?