In Norway, a study was conducted, the purpose of which was to determine the relationship between coffee consumption (measured by questionnaire), and the level of cholesterol, which was established during the second screening in Tromsø. After screening 33 men with hypercholesterolemia have been incorporated in the 10-week study. They were randomly divided into groups, one of which continued normal coffee consumption, the other completely stopped drinking coffee, the third stop drinking coffee for 5 weeks, and then again began to drink coffee, consuming or coffee made on the national method, or filtered. The results confirmed the relationship between coffee consumption and increased cholesterol levels. What design of the study was conducted