The goals of this study were to identify any associations between fecal immunochemical test (FIT) sample collection errors and specific demographic factors (possible predictors) of participants and clock-drawing test outcomes (as a screening test for cognitive impairment). Patients going in for a colonoscopy were given a choice of 5 different FITs to collect a stool sample. The clock-drawing task was part of a questionnaire that the patients had to complete. Inaccuracies occurred both in the documentation of the date of the stool collection and in the collection itself. About 2  independent raters, employing 2 standard criteria, evaluated each clock drawing. The 1,448 people that submitted a clock artwork had a mean age of 63 and were predominantly female (63%). A majority (83%) of the people in this sample were White, while 6% were Black and 24% were Hispanic. The Mendes-Santos test revealed that 292 patients had cognitive impairment. When comparing the results of the two clock drawings, the kappa value was 0.79 (P<.001). Being female (adjusted odds ratio [AOR] 1.64; 95% CI, 1.09-2.48), having fewer than 8 years of schooling (adjusted odds ratio [AOR] 3.40; 95% CI, 1.87-6.18), and having an abnormal Mendes-Santos method clock score (adjusted odds ratio [AOR] 1.65; 95% CI, 1.08-2.54) were all associated with significantly more errors in FIT collection Errors in FIT collection were made not only by those with abnormal clock drawing but also by those with normal clock drawing among the individuals who did not have dementia. Errors in the FIT collection were more likely to occur if the subject was female, had less than an eighth-grade education, or had an irregular clock drawing as rated by the Mendes-Santos method.