Comparing colonoscopy, sigmoidoscopy and fecal occult blood test for colorectal cancer screening

Study hypothesis: Comparisons of attendance, detection rates and acceptability of total colonoscopy, flexible sigmoidoscopy and fecal occult blood test (FOBT) as primary screening tests for colorectal cancer.
Primary outcome(s): Attendance and detection rate to total colonoscopy, flexible sigmoidoscopy and FOBT as primary screening tests.