Another patient is asked to check his fasting glucose until his next scheduled clinic visit which is about 3-1/2 months away (100 days). Patients seldom complete all the appropriate steps (fasting, blood draw, test, record in log). The patient successfully completed all steps 20% of the time in the past and no behavioral change is expected.
Question: A low number of checks (<=15) makes the data clinically useless. What is the probability that the patient checks 15 or fewer times?