The goal of the proposed study design is to develop and gather validity evidence of a theoretical test about cognitive skills which are important when performing Chest Tube Insertion (CTI). This study consists of two parts:

• The development of the theoretical test and its items. The test content will be based on a broad literature search, and on semi-structured interviews with content experts.
• The subsequent collection of validity evidence for this theoretical test and final selection of the test items, by testing groups that differ based on their expertise. The item analysis and observed difference in mean score between the groups will provide the validity evidence.

Inclusion Criteria:

• Content experts will be recruited from the departments of surgery, pulmonology, and emergency medicine of various hospitals in Flanders and the Netherlands. They must have finished their residency training and be actively involved in training of junior physicians. A maximum of six experts will be recruited, and a minimum of one physician from each department will be included.
• The novice group will attract medical students at Ghent University, within their 5th or 6th year of undergraduate training, while having no experience with CTI.
• The intermediate group will include residents of the departments of surgery, pulmonology and emergency medicine of Ghent University Hospital, within their 1st - 3rd year of residency training and must have placed less than 20 chest tubes themselves.
• The experienced group will be recruited from the departments of surgery, pulmonology, and emergency medicine of Ghent University Hospital. They must have finished the residency training in their respective fields and must have performed more than 20 CTI independently. The content experts will not be eligible for participation.

Exclusion Criteria:

• For the novice and intermediate group: having to much experience in CTI.