Lecture-based instruction in conventional nursing education comprises receptive learning that does not require special activities from learners; it is an instructor-centered method focused on delivering general knowledge and requiring rote memorization. Thus, it has been reported as inappropriate in helping learners improve their ability to integrate and apply knowledge independently, as well as in promoting higher-order thinking skills [1].

In a rapidly changing medical environment, nursing education is to cultivate nurses who can solve common problems in cooperation with various fields. In order for a nursing organization to operate well, effective teamwork of team members is required to achieve a common goal, and recognition of team goals and continuous self-development related to work and formation of cooperative relationships with teammates are necessary [2].

Team-based learning is a teaching method that leads to solving presented problems through interaction between team members in this cooperative relationship [3], and it supports learners to become a learning team that produces the best results by interacting with them in the thinking process of evaluating and applying new information in practical problem situations [4].

Nursing researchers have also reported that applying team-based learning in the classroom improves learners' perceptions, academic achievement, class satisfaction, and problem-solving skills [5,6]. Leadership is an important input element that influences team-based learning outcomes [7]. Thus, the focus of research has shifted from the traditional concept of leadership as the individual influence of a team leader to the concept of horizontal or collective leadership [8], also referred to as shared leadership [9]. The literature's recent focus on shared leadership is for the following reasons. The work situations and environments encountered by groups and individuals within them are becoming more complex and diverse, significantly limiting the scope of leadership that a single leader can practice. Moreover, transitioning organizations' operations to a knowledge-based structure provides individual members with increased autonomy. Research has mainly focused on corporate organizations despite the importance of shared leadership [10]. Shared leadership is a dynamic process in which members interact to achieve team goals, and it refers to the exercise of leadership by the entire member rather than the concentration of influence within the team on one person [11]. This is a phenomenon that is distributed and shared among several leaders rather than individuals, and can positively influence each other to strengthen the capabilities within the team [9].

Although various educational methods applying team-based learning in university education have been developed, researchers have only recently begun to report the positive effects of shared leadership on performance in team-based learning. Chae [12] found that shared leadership scores increased significantly after team-based learning for 48 second-year nursing students. Han [13] examined team-based learning among 99 first-year nursing students and revealed that shared leadership had a significant effect on team performance, showing a significant correlation. Teams demonstrating shared leadership can facilitate smooth communication, promote information sharing among team members, and increase participation, thereby improving team performance [14]. Therefore, it is necessary to examine the effect of team-based learning experiences on shared leadership and team performance for nursing students in nursing situations where team-level performance improvement is required.

Recently, in the rapidly changing medical environment, interest in team performance in addition to individual performance within the organization has been increasing, because the presence or absence of a systematic and efficient team has become important. Team performance can be defined as an achievement achieved by the team and an activity that strives to achieve the team's goals at the same time and focuses on the subjective perception of the team members rather than objective indicators such as the appropriateness of the team's performance achievement efforts recognized by the team members [15]. In team-based learning, team performance appears through team learning or activity processes, and it can be said that it is the level of achievement achieved by the team, which can be measured through team goal achievement, team member attitude, cooperation, and satisfaction [13].

Unlike self-efficacy, which is generally considered a variable that affects individual learners' academic achievement, satisfaction, or learning motivation, team efficacy is a key predictor of team performance as a derivative of self-efficacy. Individual team members' trust in their teammates, motivation, and performance when cooperating with their team can influence team efficacy, which is why team efficacy can be regarded as a concept distinct from individual-level variables. Team efficacy is a belief in a team's ability to perform its job successfully and is used as a major variable in predicting team performance in various environments where team systems are allowed, such as schools, businesses, sports organizations, and military organizations [16]. Team efficacy is a concept that has recently emerged, and most of the studies are from the environment of sports games or the military, where the team is the basic unit of activity. Team efficacy is being studied as a key variable in predicting team victory, that is, team performance, in the sports field of team that leads to team victory in competition with other teams by forming a team and demonstrating teamwork [17]. In the university's classroom environment, as team project learning and cooperative learning are strengthened, research on team efficacy is being conducted as a variable that predicts team performance beyond individual achievement [16].

A study analyzing team efficacy, individual effort, collective effort, teamwork, and patient satisfaction among 149 nurses revealed significant correlations among all variables, and each factor ultimately had a positive effect on patient satisfaction [18]. Kwon [16] found that team efficacy was positively correlated with team exam scores in university project-based courses. When fourth-year nursing students received team-based simulation training, team efficacy and problem-solving ability were significantly improved compared with the control group that received individual simulation practice [5].

Recent studies on the effectiveness of team-based simulation training among nursing students have reported that it is an effective educational strategy that enables students to gain experience in non-technical skills such as clinical judgment, decision-making, collaboration, and nursing practice [19].

Learning about team roles and dynamics through team-based simulation training can help develop the team competencies that future nurses must possess [20]. Effective functioning of nursing organizations depends on team members' shared understanding of teamwork and common goals, as well as their ability to form cooperative working relationships [2].

Numerous studies on team-based learning have been conducted; however, research measuring team-level performance among nursing students remains scarce. In line with the changing nursing environment, nursing education research that applies team-based learning to predict performance using the team as the unit of analysis beyond nursing students' individual-level achievements is needed. Accordingly, this study examines how shared leadership among team members affects team performance during learning and collaboration. It also explores whether team efficacy, in association with team performance, encourages team-based learning and leads to successful experiences. This study provides foundational data for creating effective learning strategies for students to experience team performance through successful team-based learning in nursing education.

This study analyzed the effect of shared leadership on nursing students' team performance in team-based learning and the mediating effect of team efficacy in this relationship. Thus, this study provides foundational data for creating effective learning strategies to enhance nursing students' team performance through successful team-based learning.

In this study, shared leadership among nursing students in team-based learning was measured using a five-point scale, yielding a score of 4.71. This is higher than the score (6.04 on a seven-point scale) reported by Han [13] for team-based learning with 99 first-year nursing students using the same tool. Furthermore, Hwang [27] measured shared leadership among 194 clinical nurses working in general hospitals and reported an average score of 3.91 on a five-point scale. Moreover, Hwang [28] measured shared leadership among 880 employees of companies and research institutes operating under team systems and reported a score of 4.11 on a five-point scale. Lee and Woo [10], focusing on special forces organized in teams in the military, reported a score of 4.32. Organizations operating in teams exhibited higher levels of shared leadership than clinical nurses, and shared leadership was high during team-based learning, as in the present study. Carson et al.[29] stated that higher levels of factors associated with the internal environment (e.g., shared purpose, social support, and voice) led to higher levels of shared leadership within the team, whereas team coaching by external leaders had a positive correlation with shared leadership in the team. In the present study, studies examining nursing education applying team-based simulation learning tended to show high levels of shared purpose and voice, whereas team coaching was conducted under the guidance of an instructor (or professor), thereby showing higher levels of shared leadership compared with other organizations.

In this study, shared leadership had a significant positive effect on team performance during team-based learning. This result aligns with previous studies on university students [13,30] which found that shared leadership positively impacts team performance and efficacy. Members of teams with active shared leadership operate in an environment where they both lead and follow their teammates, perform tasks, and enhance team efficiency through smooth coordination. Furthermore, shared leadership can improve team performance by promoting information sharing, active communication, and participation among team members [10]. Team members have a collective influence on one another [30]. As the present study conducted team-based learning, not a single leader but all team members jointly practiced horizontal leadership, thereby positively affecting the shared goal of team performance and improving satisfaction with team-based learning. Based on these findings, this study suggests that mutually shared leadership among team members in university team-based learning can affect team-centered learning outcomes. Thus, teaching and learning methods that apply team coaching are required to encourage mutual participation and role fulfillment among all team members. Moreover, this study revealed that team efficacy partially mediated the relationship between shared leadership and team performance. This implies that shared leadership induces mutual trust and confidence among team members throughout the collaboration process, leading them to achieve team goals and increasing their satisfaction with team-based learning.

Team efficacy has a crucial impact on team members, fostering mutually supportive and cooperative attitudes, and active, positive relationships that also help improve team performance [31]. Gully et al. [32] conducted a meta-analysis on the relationship between team efficacy and team performance. They revealed that team efficacy was influenced by team members' motivation, beliefs, and performance and that its impact on performance was stronger when efficacy was perceived at the team level rather than at the individual level. Hwang [27] analyzed the mediating role of team efficacy in the relationship between shared leadership and team creativity, a team performance variable, targeting a corporate research team operating under a team-based structure. The results revealed that shared leadership had a positive effect on team creativity, and the mediating effect of team efficacy was statistically significant. Lin et al. [33] studied whether team efficacy and team self-esteem mediated the relationship between corporate social responsibility and team performance, targeting 801 members across 172 corporate teams. The results showed that corporate social responsibility had a positive effect on team performance through team efficacy and team self-esteem. Lee and Kee [34] conducted a study of 327 public officials who voluntarily joined and participated in officially registered study groups within the local autonomy's continuous learning system. They examined the predictive power of team efficacy through study group activities on learning satisfaction, which is a learning outcome, and discovered that public officials with high team efficacy showed high learning satisfaction. Lee et al. [35] analyzed the effects of team efficacy and metacognition on learning outcomes such as satisfaction and problem-solving skills. Following a semester-long team-based, problem-based learning activity with 45 second-year university students split into nine teams. The results showed that team efficacy positively impacted learning satisfaction among the learning outcome variables, serving as a significant predictor, thereby supporting the findings of this study. Team performance can be evaluated in various aspects such as learning satisfaction, problem-solving ability, and team creativity, as previous studies have shown. In this study, learning satisfaction was set as a team-level variable as an indicator of team performance, but actual data collection and analysis were based on individual team members' survey responses. Team performance refers to the experience of team members cooperating and interacting, and striving to achieve learning goals to solve patients' problems presented in the simulation training. Therefore, team performance measurement was based on individual responses, but it reflected the experience of team members to achieve learning outcomes through cooperation and interaction by evaluating interest in simulation training, improvement of problem-solving ability through team learning, the degree of achievement of learning goals, communication between members, and knowledge improvement through cooperation. As can be seen from the definition of team performance, these measurements and evaluations refer to the collective team beliefs that team members perceive about the organization, so it can be confirmed that there is a certain ambiguity in the measurement process. Therefore, in order to more clearly define team performance in team-based learning in future studies, it is necessary to supplement the concept by considering objective indicators and qualitative aspects of the results produced by team members.

As revealed in previous studies, team efficacy in team-based learning and organizational activities serves as a mediating variable with a positive effect on team performance variables.

This indicates that team performance improves when team members participate in the activities with a positive belief in their team. In the team-based learning applying simulation training for nursing students conducted in this study, not a single leader but all team members practiced horizontal leadership and achieved a shared goal by distributing and performing roles through mutual communication, aiming to solve nursing problems. This increased mutual positive beliefs, and such team efficacy might have played a mediating role in improving team performance.

This study analyzed the effect of shared leadership on nursing students' team performance in team-based learning and the mediating role of team efficacy in this relationship. The findings revealed that shared leadership had a significant positive effect on team performance in team-based learning, and team efficacy partially mediated the relationship between shared leadership and team performance. The contributions of this study are as follows.

This study suggested that providing measures to enhance team efficacy among team members during team-based learning in universities may positively affect team performance and team efficacy, thereby possibly producing effective learning outcomes. Moreover, this study suggested that when implementing team-based learning utilizing simulation training for nursing students, shared leadership competency should be incorporated into the evaluation index.

This study has limitations regarding generalizability, as it examined nursing students from a single university. Therefore, replication studies in other contexts and different samples are warranted and team-based learning utilizing simulation training requires evaluating team performance using both qualitative results and objective indicators. Moreover, research on the effects of specific methods for improving team efficacy in team-based learning and on team coaching is required to encourage shared leadership.