A novel drug (Uelostatin) was tested for its cholesterol-lowering properties by carrying out an experiment using 50 volunteers. First, plasma cholesterol concentrations were measured to establish a pre-treatment value. The volunteers were then given the drug once daily for one month, after which time their plasma cholesterol concentrations were again measured. The cholesterol concentrations from the 50 volunteers before and after the treatment are provided in the enclosed Excel spreadsheet. You are required to investigate the following: The pre-treatment value was assumed to be at least 6 mmol/L. At the 95% level of confidence, does he have enough evidence to disprove this assumption? Select a suitable statistical test to assess whether the drug had a significant effect on plasma cholesterol levels.