A recent study evaluated the effectiveness of 'reassuring messages' targeted at reducing the fear of physical movement typically present in patients recovering from bouts of work-limiting, occupation-related low back pain.

The study consisted of enrolling high-voltage utility workers presenting to the company's occupational clinic for treatment for work-related low back pain.Individuals were randomly allocated to one of two groups based on the treatment received.The study investigator (physician) provided medical care to subjects in both groups.The subjects in the first group were given the 'reassuring messages' in addition to usual care.The subjects in the second group only received usual care.The primary outcome was measured using the Oswestry Disability Index (ODI), and was assessed at the end of the treatment program.The study investigator administered the follow up ODI three weeks after the intervention.

a.Assuming the null hypothesis is that there is no association between therapy involving "recurring messages" and fear of physical movement, write a research hypothesis statement that reflects the research question being assessed.

b.Which study design best describes the above study? Explain your choice.

c.What potential type(s) of bias can you identify from the study above (mention at least one)? AND suggest ways to address them

d.Specify the exposure (independent) variable(s) in the study

e.Specify the outcome (dependent) variable in the study

f.What kind of statistical test would likely be used to test the hypothesis for this study and explain why?

g.If the investigators had to compute sample size for this study a priori, what key factors would have been needed?