clinician in cardiovascular medicine wanted to establish whether administering various doses of the antioxidant vitamin C has an effect on the expression of the adhesion molecule ICAM-1. They carried out a randomised double-blind trial, using male subjects aged 20-45. Subjects were either given placebo (0 mg; no vitamin C), 90mg vitamin C (Recommended daily intake for this demographic), 180mg (twice the recommended daily intake) or 250mg vitamin C for 6 weeks after which a blood sample was taken and the serum tested for sICAM-1 using an ELISA assay. The mean concentration of sICAM for each volunteer is shown in table 1.

Table 1. sICAM-1 levels in male volunteers after taking Vitamin C supplements for 6 weeks

sICAM-1 levels in volunteer serum (ng/ml)
Placebo (0 mg)	90mg vitamin C	180mg vitamin C	250mg vitamin C
483	453	429	435
457	442	435	426
521	392	417	404
534	497	473	417
463	475	462	419
456	489	479	444
479	451	446	425
437	449	462	419
473	432	429	452
452	457	462	483
441	434	441	429
427	430	433	433
481	495	491	473
477	441	448	435
498	434	439	441
432	483	487	435
465	442	449	453
473	453	458	406
442	482	472	431
469	471	483	444

1. Present basic descriptive statistics for measures of mean and spread of data.
2. Identify a suitable statistical test to assess the data and explain your rationale for this choice.
3. State both your null hypothesis and alternative hypothesis for the test you have chosen.
4. Explain your results in the context of the research study described