In the first stage, all participants will be explained about the research and their consent will be obtained. 'Personal Information Form' will be filled out for the relatives of the patients whose informed consents are obtained and who agree to participate in the study. Then, 'Information Questionnaire' and 'State Anxiety Scale' will be administered to all patient relatives as a pretest.

In the second stage, the relatives of the patients who will undergo colonoscopy will be trained with the Teach-back technique.

In the third stage, 'Information Questionnaire' and 'State Anxiety Scale' will be applied as posttest after the training. In addition, 'Satisfaction Evaluation of Teach-Back Method' will be performed.

In the first stage, all participants will be explained about the research and their consent will be obtained. 'Personal Information Form' will be filled out for the relatives of the patients whose informed consents are obtained and who agree to participate in the study. Then, 'Information Questionnaire' and 'State Anxiety Scale' will be administered to all patient relatives as a pretest.

No intervention will be made in the second stage. The routine process in the hospital will continue.

In the third stage, 'Information Questionnaire' and 'State Anxiety Scale' will be administered to the relatives of the patients in both intervention and control groups as posttest after the training.

The relatives of patients who will undergo colonoscopy will be trained with the teach-back technique.

This form was prepared by the researchers in line with the literature and includes questions questioning the demographic characteristics of the patients' relatives such as age, gender, socioeconomic level, etc. This form will be used before the training

This form consists of questions that will measure the level of knowledge of the patients' relatives about the preparation that should be done before colonoscopy. A literature review will be conducted and 20 multiple-choice questions will be prepared by the researchers. Expert opinion will be obtained from a total of 5 faculty members working in the department of nursing principles in the preparation of this form. Then, the form will be finalised after the necessary arrangements are made. In the form consisting of multiple-choice questions with one correct answer, each question has a value of 5 points. Caregivers can get at least 0 and at most 100 points from the knowledge test. Increasing the score means that the knowledge is sufficient. Questions with incorrect answers are considered as topics to be prioritised in training.

This form will be used before and after the training.

This scale was developed by Spielberger and colleagues (1970). The scale was adapted into Turkish by Öner and Le Compte (1998). The scale consists of 20 questions and it is a scale that determines how the individual feels at a certain moment and condition. In the state anxiety scale, the response options collected in four classes are: (1) Not at all, (2) A little, (3) A lot and (4) Completely. The constant value for the State Anxiety Scale is 50. The scores obtained in the state anxiety scale theoretically vary between 20 and 80 points. In the evaluation of the scale, it is accepted that those who score below 36 have no anxiety, those who score between 37 and 42 have mild anxiety and those who score 42 and above have high anxiety.

This form will be used before and after the training.