A Conjoint Analysis of Preferences on Medical Endoscope After-sales Service

Background: Medical endoscope instruments are minimally invasive, and they are widely used to investigate symptoms or help to perform certain types of surgery. This study investigates and de�nes a comprehensive set of attributes, to measure the after-sales service of medical endoscopes. The set of attributes help customers communicate their real needs with suppliers, and guide suppliers to develop the right products and services to ful�l customer demands. Methods: Based on literature review and the �ndings from the Delphi study, we identi�ed 5 factors (attributes) that best described the expectations on the after-sales service of medical endoscopes. Using conjoint analysis, a set of 16 combinations (also named as cards or pro�les) of the factor levels were generated in orthogonal design and used to develop the questionnaire. We administered the cards to 65 medical staff and 56 medical engineers across 50 Chinese hospitals, asking them to assign a preference score to each card. The utility value of each factor level was estimated and attribute importance values were obtained. Results: Attribute importance and utility values of factor levels were analysed at the aggregate level, occupation level, and medical institution level. (1) At the aggregate level, the �ve attributes were ranked in the order of importance values, the most important one is “maintenance response” and the least important is “maintenance e�ciency”. (2) Medical staff and medical engineers ranked the �ve attributes in the same order. However, medical staff paid more attention to "maintenance response" and medical engineers paid more attention to "maintenance quality". (3) At the medical institution level, primary hospitals paid more attention to "maintenance price", while tertiary hospitals paid more attention to "maintenance quality". Conclusions: In this study, the utility values and attribute importance that affected the after-sales service level of medical endoscopes were obtained using conjoint analysis. The research results were consistent with the actual market situation of medical endoscope service. In general, this study provides a more scienti�c solution for hospitals in choosing after-sales service of medical equipment, and it also helps manufacturers and suppliers improve the after-sales service.


Background
In medical endoscope market, service demand and product demand are two key factors in uencing the choice of medical endoscopes.Medical endoscopes are important tools to perform minimally invasive clinical surgery and examination.Medical endoscopes are also commercial products that have the attributes of medical devices.As a medical device, endoscopes must go through risk assessment which is an ongoing responsibility and must be managed as a top priority by manufacturers, suppliers (agents selling endoscopes), and hospitals.The customer service provided by manufacturers or suppliers for endoscopes is not only an after-sales service for a commercial product, but also a high quality of service and support for safeguarding, repairing and maintaining endoscopes.The quality of customer service is an important factor affecting the hospitals' decision in purchasing medical endoscope products.The State Food and Drug Administration has introduced a number of national and industrial standards, to audit the quality of medical endoscope products, however, the standards of evaluating the services provided to medical endoscopes do not exist [1][2][3][4][5][6][7].In order to improve the service quality of medical endoscopes, several industry associations in China have explored various evaluation methods, and also conducted multiple demand surveys on the after-sales service of medical endoscopes.For example, Shanghai medical equipment quality control center conducted service evaluation and demand analysis of medical endoscopes as early as 2011 year [8].Ranking method is a popular method used to analyse the service quality of products.To make the ranking, questionnaire is distributed to collect the factors and information that in uence ranking.Service Multiple factors, such as features, functions and bene ts, make up a product or service.To evaluate the quality of after-sales service provided to medical endoscopes, we need to develop a method that considers a comprehensive list of the attributes associated with medical endoscopes, and determines the most in uential or important combination of attributes [9][10][11][12].
In this study, we used conjoint analysis to analyse and evaluate the after-sales service provided to medical endoscopes.Through a survey with 121 medical staff and engineers working in 50 hospitals in China, we analysed speci c needs on endoscope's after-sales service, from the perspectives of medical staff, medical device engineers, tertiary hospitals and primary hospitals.In the hospital context, we further explored the factors in uencing the decision making by purchasers, end users and maintenance managers when choosing endoscope products and services.The research provides guidance to buyers in purchasing medical endoscopes; it also offers a framework to set up standards on after-sales service, and ultimately it promotes the development of an economic and technological ecological environment in endoscopy industry [13][14][15][16].

Respondents
In this study, a random sampling method was used to select 50 hospitals in different provinces in China; these hospitals have purchased and used medical endoscopes in the last 5 years.The front-line medical staff and medical engineers who had experiences of using or managing endoscopes were appointed as subjects to rate a set of pro les (or cards) in the conjoint analysis.Each subject must have more than 3 years of working experience in using or managing medical endoscopes [17].

Experimental method
Experimental design refers to the process of generating speci c combinations of attributes (factors) and levels evaluated by respondents.In this study, conjoint analysis and orthogonal design were used for experimental design and statistical analysis.Conjoint analysis is a survey based statistical technique used to help determine how people evaluate different attributes of products or services, such as functions and features.Conjoint analysis presents choice alternatives between products or services de ned by a combination of attributes; it can also be used to determine both the relative importance of each attribute and which levels of each attribute are most preferred.In conjoint analysis, each pro le describes a complete product or service, and it is de ned by a different combination of factor levels for all factors of interest.The full-pro le approach is used in conjoint analysis, where respondents score, rank or order a set of pro les.If the number of combinations of factor levels is too large, a fractional factorial design is introduced to deal with the problem.A fractional factorial design, also called orthogonal design, selects a fraction of all possible combinations of factor levels, to capture the main effects for each factor level.The Orthogonal design is typically a starting point of a conjoint analysis [18][19][20].The rest of the combinations that are not used in the orthogonal design are called holdout pro les.
In an orthogonal design we assume there are K factors and each factor has n levels, i.e., t1, t2, …, tn.If this design meets two conditions: different levels of each factor appear the same number of times in the test (equilibrium); different combinations of factor levels for any two factors appear the same number of times in the test (orthogonality), this design is called orthogonal design.The orthogonal design is used to generate an orthogonal array, which can not only make the distribution of test points very uniform, but also reduce the number of tests.In this study, orthogonal array is used to generate factor-level combinations of pro les, also called cards, which are rated by the respondents (also called subjects).
A random sample of subjects (respondents) from the target population is selected to evaluate the set of pro les, or cards.The subjects assign a preference score to each pro le based on intuitive experience.The reference score can be a Likert scale, or a number between 1 to 100.Alternatively, subjects can assign a rank to each pro le using a number from 1 to the total number of pro les.
Analysis of data from the survey results in a utility score, called part-worth, which provides a quantitative measure of preference for each factor level.Each factor or attribute has multiple levels; we are interested in the preference value or relative importance of each attribute.The calculation of attribute importance value is presented in a multivariate framework [21,22]: where Z(x) is the overall utility for a card (pro le), rated by the subjects; Uij represents the part-worth utilities for factor level j of factor i; Xij represents the level of a factor (attribute); it is a categorical variable, measuring weather factor i at level j is absent (=0) or present (=1) in this card (pro le).K is the number of factors; n is the number of levels in each factor.Uij is the value of interest, and it is estimated using Ordinal Least Square method using the linear regression model.e ij is the stochastic error term.
Once utility score Uij is obtained, the range of the utility score for a factor i is calculated as the difference between the maximum and the minimum party worth utility: The importance value of factor (attribute) i is expressed as: The factor (attribute) importance value ranges between 0 and 1.The greater the value, the more important of the factor in the evaluation system of endoscope after-sales service.
In this study, the combinations of different factors and related levels of medical endoscope were created based on the results from the Delphi method [23].The set of pro les (cards) were created through orthogonal experimental design, which required the subjects (respondents) to assign preference to each combination intuitively based on experience; then the importance of each factor and the effect of factor level are calculated using equations ( 1)-(3) [24].

Research process
Factors and levels of service preference of medical endoscope An initial set of factors and levels of factors were chosen from literature review to de ne after-sales service of medical endoscope.This set of factors and levels were evaluated, ltered and revised by a group of experts through two rounds of Delphi method [23][24][25][26].A re ned set of factors and levels of factors were identi ed from the Delphi method for medical endoscope after-sales service, including maintenance quality, maintenance price, maintenance response, maintenance e ciency and service provider.Each factor contains multiple levels, and the meaning of each factor and level is shown in Table 1.For example, there were three levels of maintenance quality, de ned as "the same fault happened within 6 months", or "the same fault happened between 6 months and 12 months", or "the same fault happened after 12 months.Maintenance price varied with hard endoscope and soft endoscope, as de ned at the three levels.Similarly, maintenance response rate and e ciency were also measured at three levels.Service provision was classi ed as the service provided by the original manufacturer, or by the third-party service agents.

Orthogonal experiment design
The full-pro le approach of conjoint analysis generates 162 (3 × 3 × 3 × 3 × 2) pro les resulting from all possible combinations of the factor levels.The total number of 162 became too big for respondents (subjects) to rank or score in a meaningful way.To solve this problem, the orthogonal design was used to reduce the number of combinations, and to retain the main effects of combinations which re ect the service attributes of medical endoscopes.The orthogonal experimental design was carried out in SPSS software, and a reduced set of 16 pro les (cards) were generated.The 16 cards represented different combinations of factor levels of medical endoscope, and one of the cards was shown in Figure 1.The number of 16 pro les was small enough to include in a survey but big enough to assess the relative importance of each factor [27].

Data collection
The questionnaire contained three sections: (a) demographic information of the respondents, including employer information, occupation, number of years of working, etc.; (b) an explanation of the after-sales service attributes and levels, as well as the type of method used to assign preference scores; and (c) the main body of the questionnaire, presenting the 16 cards to each respondent and asking them to assign a preference score to each card.Each respondent was asked to answer the question of "how likely would you choose the above service?"using the ten-level Likert scale (score 1-10).
In this study, medical staff who used endoscopes to perform diagnosis or treatment, and medical engineers who worked in hospitals and had responsibilities of maintaining and repairing endoscopes were invited to participate the survey.The respondents must have had over 3 years' working experiences, and 125 respondents from 50 Chinese hospitals were selected to evaluate medical endoscope after-sales services.A total of 125 questionnaires were sent out and 121 were recovered, of which 121 were valid, with an effective response rate of 96.8%.

Results And Discussion
The group of 121 respondents consists of 65 medical staff and 56 medical engineers.Among the respondents, 27 were from the primary hospitals and 94 were from tertiary hospitals.The Pearson correlation coe cient between the observed and estimated preferences (the observed and predicted rank orders for the holdout pro les) was 0.875 and the Kendall's tau was 0.662 (p < 0.001), showing the results were reliable and valid.Table 2 showed the utility values and attribute importance scores of endoscope after-sales service rated by different groups of respondents, i.e., medical staff, medical engineers and the whole population of both medical staff and medical engineers.

Preferences of after-sale service of medical endoscope
Using equations ( 1)-(3), we obtained importance values of service attributes which re ected the hospitals' awareness of the importance ranking of service attributes.According to the results of the conjoint analysis, the major factor in uencing medical staff and engineers' satisfaction on after-sales service is the "maintenance response"(23.665%),followed by "maintenance quality"(22.165%),"maintenance price"(20.961%),"service providers"(17.873%), and "maintenance e ciency" (15.336%), as shown in Table 2.
In Table 2, the utility values of the attribute level re ected the respondents' preference for the service selection.The greater the absolute value of the utility, the stronger the preference.The whole population's preferences on endoscope after-sales services had the following features: for the attribute of "service provision", there was a big difference between the two factor levels.There was a stronger preference on the "service provided by the original manufacturer" which received a utility value of 0.373, while the "service provided by the third party" received a negative utility value of -0.373.It seems that medical staff and engineers were reluctant to use the third-party service providers.Under the attribute of "maintenance quality", the utility values of the three factor levels were all negative, indicating that medical staff and engineers were not satis ed with the maintenance quality, regardless of the frequency of the same fault occurrence.Compared with the other two attribute levels, the medical staff and engineers were more willing to accept the moderate level of maintenance quality, i.e., 6 months ≤ same fault ≤ 12 months, as the absolute value of this attribute level is the highest (3.690).Regarding the attribute of "maintenance price", the utility values of the three factor levels were all positive, and the absolute values were relatively large, which showed that "maintenance price" was positively related to respondents' preferences, and the correlation intensity was relatively high.The preference on the price level of "hard mirror ≤ 10,000 yuan, soft mirror ≤ 30,000 yuan" received the highest utility value of 1.881, showing that hospitals preferred to receive better maintenance services at the expense of a higher price.The attribute "maintenance response" had three levels of positive utility values, of which the utility value of "3 days < maintenance response ≤ 7 days" received the highest score of 2.394.This means that moderate maintenance response and receive maintenance response within 7 days was most describable.The attribute of "maintenance e ciency" also had three levels of positive utility values, of which the factor level "10 days < maintenance time ≤ 20 days" received the highest utility value of 1.634, showing that this level of e ciency was most desirable for medical staff and engineers.

Analysis of preferences on service pro les
Using the orthogonal design, 16 endoscope after-sales service pro les de ned by 16 combinations of the attribute levels were evaluated, and the attribute important scores were obtained.The optimal results were derived from the conjoint analysis: the most desirable endoscope after-sales service pro le was: "6 months the same fault ≤ 12 months", "hard mirror ≤ 5000 yuan, soft mirror ≤ 10000 yuan", "response ≤ 1 day", "maintenance time ≤ 10 days" and "service provided by the original factory"; while the least favorable service pro le was: "the same fault ≤ 6 months", "hard mirror ≤ 20000 yuan, soft mirror ≤ 50000 yuan", "3 days < response ≤ 7 days", "maintenance ≤ 20 days" and "the third party provides services".The results showed that response time, maintenance time, maintenance price and service providers were important to medical staff and engineers, who tent to choose the service provided by the original manufacturer, with quick response time, short maintenance time and low price.Compared with the other four attributes, a moderate level of maintenance quality (6 months the same fault ≤ 12 months) was generally acceptable to the medical staff and engineers.This was attributed to the following reasons: medical endoscopes are operated in human body with a high frequency of use, and the operating environment is complex, therefore, there is usually a high fault or failure rate, with an average maintenance frequency of once per 12 months.The least favorable service pro le was characterized by the "third party service providers" and poor "maintenance quality" ("the same fault ≤ 6 months"), which was consistent with the actual expectations on endoscope after-sales service, i.e., there was a strong resistance on the third-party post sales service and poor maintenance service.

Analysis of preferences by respondents with different occupations
Taking the occupation of respondents as a variable, we analysed and compared the relative importance of attributes, and factor utility values, rated by medical staff and medical engineers (see Table 2).The results showed that there was no signi cant difference existing in attribute importance or factor utility values between the two groups.The ranking of attribute importance was consistent between the two groups, showing that the selection preferences were identical in terms of service provision, maintenance quality, maintenance price, maintenance response and maintenance e ciency.The utility values of factor levels varied between medical staff and engineers.When choosing service provision, both groups preferred the service provided by the original manufacturer, but medical engineers felt that there was a small difference between the maintenance service provided by the original manufacturer and the service provided by the third-party provider, while medical staff thought that the difference was large.The different opinions were re ected in the utility values; 0.45 and -0.45 were scored by medical staff, and 0.313 and -0.313 were rated by engineers.
In terms of maintenance quality, both medical staff and engineers chose level 2, "6 months the same fault ≤ 12 months", but the utility values of this factor level was different.Doctors and medical engineers both chose maintenance price level 2, i.e., "hard mirror ≤ 10000 yuan, soft mirror ≤ 30000 yuan".
Both medical staff and engineers preferred the maintenance response level 3, i.e., "3 days < response ≤ 7 days", while medical engineers were also willing to accept level 2, i.e., "1 day < response ≤ 3 days".The scores assigned by medical engineers to levels 2 and 3 were 2.280 and 2.284, with a minor difference of 0.004.Medical staff rated levels 2 and 3 by 2.392 and 2.533, indicating that they were more inclined to accept level 3 rather than both levels 2 and 3.In addition, doctors and medical engineers were more willing to accept the maintenance e ciency level 2, i.e., "10 days maintenance ≤ 20 days".Both groups expected a high maintenance e ciency of endoscope after-sales service.The utility scores estimated from medical staff responses were higher than the utility values derived from engineers' responses, which to an extent re ect the professional characteristics of different occupations hospitals.

Analysis of preferences by respondents from different medical institutions
Taking the type of medical institutions as a variable, we analysed and compared attribute importance, and utility values of factor levels, rated by respondents from primary hospitals and tertiary hospitals (as shown in Table 3).The two types of hospitals ranked the attributes in different orders: primary hospitals ranked the attributes as 1) maintenance response (the most important), 2) maintenance price, 3) maintenance quality, 4) service provision and 5) maintenance e ciency (the least important); while the ranking assigned by tertiary hospitals is: 1) maintenance response (the most important), 2) maintenance quality, 3) maintenance price, 4) service provision and 5) maintenance e ciency (the least important).The weight ranking of different attributes and the selection of each attribute level are also consistent.It was clear that maintenance price matters more to primary hospital than maintenance quality; while quality was more important to tertiary hospitals.The different focus was related to the overall strength and performances of different medical institutions.Primary hospitals usually had less investment in, or resources assigned to medical device services, hence, the maintenance quality was sacri ced as a trade-off to lower maintenance price.While tertiary hospitals' overall performances and capabilities were stronger so that they could afford more expensive maintenance to ensure high maintenance quality.Although there was a difference in ranking attribute importance, the most desirable after-sales service pro le chosen by primary hospitals and tertiary hospitals was identical, as de ned by "service provided by the original factory", "6 months the same fault ≤ 12 months", "hard mirror ≤ 10000 yuan, soft mirror ≤ 30000 yuan", "response ≤ 7 days" and "7 days maintenance ≤ 20 days".

Discussions
The in uences of attributes on medical endoscope after-sales service In the process of evaluating after-sales service of medical endoscopes, medical staff and engineers put stronger emphasis on two attributes, i.e., maintenance quality and maintenance response, and less attention was given to service provision, maintenance price and e ciency.Users of medical endoscopes, represented by medical staff and engineers in this research, paid more attention to the maintenance quality of medical endoscopes, and was not willing to accept the endoscope failure during use.They preferred to high maintenance quality to ensure less device failure in a short period of time, which would cause less disruption to medical diagnosis and treatment.Medical endoscopes are important and commonly used medical devices in the medical examination process; when a malfunction occurs, the users expect prompt responses from the after-sales service providers to resolve the problem, and to maintain continuity in examination and treatment.
Since public hospitals are non-pro t institutions and bene t from partial nancial subsidies from governments, they had the advantages of being able to afford high quality (with relative higher prices) medical endoscope after-sales service.They were not tolerant with low-price and low-quality after-sales service, nor were they interested in excessively expensive services.
Regarding the service provision, although "service provision" is a less important factor, the hospitals were resistant to "third party service providers".This is attributed to the poor standards the third-party service and the unreliable quality level.From the market perspectives, there is an expectation that the third-party service providers to provide fast response, exible, customised support at competitive price, hence become the primary after-sales service providers [28,29]."Maintenance time" is least concerned.As a medical device, medical endoscopes require high maintenance quality, which takes a relatively long maintenance time.It took a long maintenance time to repair or maintain endoscopes and this was generally accepted, especially when the service providers could offer alternative endoscopes to use.

Medical staff and engineers have different preferences on after-sales service
Hospital workers were divided into medical staff and medical engineers, and there was no signi cant difference in the ve attribute importance values rated by medical staff group and medical engineers group.Medical staff and medical engineers put strong emphasis on maintenance response, quality and price.Since medical staff was lack of knowledge on the causes or mechanisms to endoscope failures, as endoscope users, they needed prompt response from service providers, thereby to enhance their understanding of the impacts of the failure on the diagnosis/treatment, and to give them psychological support.Therefore, medical staff assigned higher preference scores to "maintenance response".However, as providers of daily maintenance of medical endoscopes, medical engineers had a better understanding of the operation mechanism and working principle of endoscopes.When the medical endoscopes malfunctioned during use, they paid more attention to the causes of the malfunction, troubleshooting the problems and proposing solutions to x the problems and avoid it in the future.With different emphasis and expectations on the after-sales service provision, medical engineers also assigned higher scores to maintenance response and maintenance quality.Furthermore, in the event of there being a failure of a endoscopes, medical engineers did not experience the same level of nervousness as medical staff, so they did not rate "maintenance response" as high as medical staff.On the contrary, medical staff, as users of endoscopes, did not understand the technical requirements of endoscope maintenance, so they believed the service provided by the original manufacturer was the best.Compared with medical engineers, medical staff assigned a higher score (0.450) to the service provision by the original manufacturer.
Primary hospitals and tertiary hospitals had different preferences on after-sales service By analysing the attribute importance rated by respondents from different medical institutions, we found that "maintenance response" was the most important factor for both primary and tertiary This is due to the similar reasons discussed above, which led to medical staff and medical engineers assign the highest score to this attribute.
With regards the second most important attribute, tertiary hospitals put more emphasis on "maintenance quality" while primary hospitals had more focus on "maintenance price".It was related to the regional economic capacity, comprehensive strength of medical institutions and operation mechanism of medical institutions.In China, most hospitals are non-pro t public organizations that are primarily funded by governments and generate revenue through service charges and medicine charges.In recent years, private medical institutions in China have developed rapidly, and some hospitals have further expanded in the form of groups and chains.In this study, it was observed that primary hospitals that rely on full funding from governments were more cautious in terms of operating expenses.This was re ected in the strong emphasis on "maintenance price", which was higher than of the score rated by tertiary public hospitals.As a high-end medical equipment, medical endoscopes were widely used in higher level medical institutions, but less used in low-level medical institutions and private medical institutions was relatively low.Having a strong orientation towards low price endoscope maintenance service put the quality of maintenance at risk, which could lead to defective endoscopes used for diagnosis or examination.This is an important issue that is noteworthy and needs prompt actions.The segmentation of hospitals classi ed hospitals into different groups, for example, the primary and tertiary hospitals; general hospitals and specialist hospitals; public and private hospitals.Primary hospitals and private hospitals are more sensitive to the price factor, than tertiary and public hospitals.Considering the further opening of China's medical market and the vigorous development of private institutions, it can be predicted that demands on high-end and low-end medical products and services will continue to co-exist in China's medical market for a long time [30][31][32][33].It is, therefore, imperative that medical product and service providers develop a wide portfolio of products and services, to meet hospitals' diverse needs, and speci cations for functions, features, service and price.

Selection and information bias
The experimental study design means selection bias and information bias might exist, which is the limitation of this research.Selection bias could result from the selection of the respondents (subjects) in the conjoint analysis, which limits the comparability between groups (medical staff and medical engineers; primary and tertiary hospitals) being studied.To reduce the impacts of selection bias, the sampling method used in choosing respondents was random, and the professionals who met the criteria had equal probability to be included in the study.Future work will expand the conjoint analysis to include more subjects, and to further re ne the conjoint analysis results.
The use of questionnaire is useful in collecting perspectives, views, and opinions on the preferences of endoscope service attributes.However, information bias may arise from self-reporting bias (such as recall bias), or inaccurate estimation.To overcome recall bias, we de ned the selection criteria to choose respondents (subjects) to participate the questionnaire, requiring them having more than 3 years of experiences of using or managing medical endoscopes, therefore, these respondents were supposed to have up to date knowledge to evaluate the service attributes.To ensure internal validity of the collected responses and to minimise the impacts of inaccurate estimation, Pearson's correlation coe cient and Kendall's tau were calculated to check the reliability and validity of the regression model and estimated utility values.
The next phase of study will involve surveys with a wider group of respondents who will rate the service attributes.In additional to the use of statistical methods, we will compare the survey data and the results from conjoint analysis with Users' Evaluation reports or Technical reports on medical endoscopes, to examine the validity and reliability of the self-reporting instrument.

Conclusions
This study obtains the important factors and weights that affect the after-sales service level of medical endoscopes by conjoint analysis method, and comprehensively analyzes the service demand of medical endoscopes from the overall level, personnel level and medical institution level.The results of the study provide a new perspective and approach for the purchase of service products and the improvement of service mode of service providers.
In this study, the attributes and attribute importance that affect the after-sales service of medical endoscopes were obtained using conjoint analysis.A comprehensive analysis of preferences on service attributes was carried out at the aggregate level, occupation level, and medical institution level.The research results provide a new perspective and approach in choosing after-sales service for medical equipment; it identi es the important attributes and helps medical device manufacturers or suppliers developing effective after-sales service.

Table 1
Endoscope after-sales service factors and levels

Table 3
Preference scores rated by respondence from different medical institutions A pro le (card) of endoscope after-sales service