Compilation E7080 of safety culture aspects. Each step is described in the following sections. In the current case, the approach to assessing safety culture was to select safety culture aspects that have been previously investigated in other research studies. Each aspect was represented in a questionnaire by a number of relevant items. The questionnaire can be found in [32]. To arrive at a measure for each aspect, an average score of the responses was calculated on the items that belonged to the aspect. All in all, 110 items represent the nine aspects in the questionnaire. The aspects were not designed using

factor analysis, instead each aspect was designed to relate to a specific sub-aspect of safety culture. The aspect could be about the effects of a safety culture or could be a prerequisite for the existence of a safety culture (see Section 2.2.). The items included for each aspect reflect different facets of the aspect. Thus, the items included were based on pre-understandings and assumptions built on theories about conditions in an organization that were proven or assumed to be related to risk and safety and different safety culture aspects. The passenger shipping study [31] was performed on six passenger/cargo ships (two high speed crafts [HSC] and four passenger/cargo ferries [Ropax]), in three shipping companies. The ships operated on

routes in the Baltic Sea and the Kattegatt. All ships sailed under Swedish flag and with Swedish crews. A total of 528 (out of 711) seafarers on the six ships completed buy Sotrastaurin the safety culture questionnaire. Questionnaire response rates, average age, and average time at sea for the respondents, number of passengers, and car capacity for each ship in the three shipping companies are presented in Table 1. During data collection the first author performed research visits of two to three days on each ship and during this time the questionnaire was administered to all crew members with the help of officers from the deck, engine, and catering departments. All crew members filled in the questionnaire independently during their shift or when off-duty and after completion Unoprostone put the questionnaire

in an envelope which was then closed. The closed envelopes were gathered in a box on board. The filled-in questionnaires were thereafter sent to the first author by mail. During the first authors visit on board she was available to answer questions from individual crew members concerning specific items in the questionnaire. It is important to accurately estimate the missing values in the questionnaire data set since this might influence the results in a way that is difficult to acknowledge when the results are later interpreted. There is a range of methods available to estimate missing data. However, two methods are generally considered to give the most accurate results: Expectation maximization (EM) and multiple imputation (MI).