1 Introduction

Due to the rapid development of information technology, the whole education system is undergoing significant transformation [1]. In 2017, the Ministry of Education of China issued the “Guidelines on Further Promoting the Development of Informatization in Vocational Education”, which stated: The aim is to implement an innovative teaching model in vocational education that integrates information technology with teaching; Teachers are encouraged to make full use of digital resources to address key points in skill training; Remote collaboration, real-time interaction, flipped classroom and mobile learning are promoted to enhance learner initiative and encourage comprehensive interaction between teaching and learning [2].

In recent years, many Chinese vocational colleges have prioritized modern educational technology as part of these reforms. While most teachers have incorporated multimedia technology into their teaching, the traditional teaching model has not been completely abandoned [3]. The English course is an important compulsory course in higher vocational colleges. However, the traditional teacher-centered teaching model has exposed various disadvantages. Teachers play a leading role in the whole teaching, while students are in a passive position [4]. Students' initiative, enthusiasm, and creativity are neglected, which results in the lack of confidence and the correct cognition of the self-ability of students.

The flipped classroom teaching model has realized the innovation of the traditional teaching model. Flipped classroom replans the time inside and outside the classroom [5]. The instructional videos and teaching materials are uploaded by teachers to the online teaching platform, on which the students learn by watching videos, and consulting the relevant information before class [6]. In class, more time is freed up for interactive and collaborative learning by group activities [7], which enhances students’ self-confidence and enthusiasm for learning [8].

Self-efficacy was proposed by Albert Bandura [9] based on social cognitive theory. Bandura [10] defined an individual's self-efficacy as their perception of their own abilities to learn or perform specific tasks at a specific level [10]. People's beliefs concerning their self-efficacy can be developed through mastery experiences, vicarious experience, social persuasion, and physiological and emotional states [11]. Academic self-efficacy refers to the belief that one can learn or act in academic situations at a given level [12]. Ever since Bandura’s research, the studies of self-efficacy have been conducted by an increasing number of researchers in various fields. Research shows that higher academic self-efficacy leads to better learning performance, stronger learning interest, and greater confidence in overcoming difficulties in the field of education [39].

Based on the above interpretation, the belief of English language learning self-efficacy in the education field refers to learners’ ability evaluation and subjective judgment on whether they can complete tasks and carry out specific activities in English learning. It involves how the confidence of the learner is on judging whether the learning task can be completed well.

According to Bandura [11], people's beliefs concerning their self-efficacy can be developed by four principal sources [11]. Mastery experiences are the most efficient means of fostering a strong sense of efficacy [11]. Outcomes that are viewed as successes raise self-efficacy, while outcomes that are viewed as failures lower them. Continuous successes make people establish self-efficacy, which will not be reduced by a temporary frustration or challenge, whereas repeated failures will even make people give up. The second influential source is through vicarious experience [11]. Observers are inspired to believe they are capable of achieving similar results when they witness people similar to themselves succeed through perseverance [40, 41]. A combination of comparisons and peer modeling can significantly influence the development of self-perceptions of competence [42]. People receive social persuasion from others as a third method of boosting their self-efficacy belief [11]. An individual who is convinced verbally that they possess the capability to dominate a particular activity is likely to mobilize greater efforts and sustain them for a longer period of time [43, 44]. Furthermore, people are influenced in part by their physiological and emotional states when evaluating their abilities [11]. People who are highly anxious, worried, and fatigued tend to underestimate their capability and decrease their motivation and confidence to accomplish tasks.

Ever since Bandura’s research, studies of self-efficacy have been conducted in various fields. The most prominent domain is education which primarily focuses on its correlation with autonomous learning, learning motivation, learning achievement, attributions, self-regulation, monitoring, strategy training, reward contingencies, online learning, and teacher education. The findings have proved that self-efficacy plays an essential role in learning, influencing an individual’s behavioral choices, thought patterns, emotional reactions, goal setting, choices of learning strategies, performance of effort toward goals, and persistence of effort in the face of obstacles.

2.3 Flipped classroom and English language learning self-efficacy

According to the four principal sources of self-efficacy which can help develop self-efficacy from Bandura [11], the formation of self-efficacy in English learning is based on students' mastery experience in learning English, students' models at each level, encouragement and suggestions from groups as well as teachers' evaluations, and the formation of positive and healthy mentality. Flipped classroom can affect the formation of self-efficacy in English learning from the above four aspects. Self-efficacy can be improved in the process of flipped classroom. It has the theoretically positive promotion of self-efficacy. The flipped classroom teaching model includes two stages: pre-class self-study and in-class collaboration [45]. The key section is group collaboration in class.

First, the learning guide prepared by the teacher before class includes progressive learning objectives, diverse standards and requirements, and exercises with different degrees of difficulty, which provides opportunities for students of different levels to experience success. When students consistently overcome obstacles or make progress, the successful experiences they gain can enhance their self-efficacy [46]. Secondly, group collaboration during class aims to achieve a common learning goal [47]. Each group member should strive together, learn from and support each other, and provide suggestions and encouragement [48]. Personal success can lead to increased motivation and self-efficacy [49]. Additionally, modeling can serve as a form of social comparison [50]. Observing others perform a task can lead individuals to believe they can do the same [51]. This is because modeling implies that observers have the necessary abilities for success [52]. Therefore, group members can obtain model demonstrations from peers at each level by observing learners with similar abilities, which can help them gain vicarious experience and develop self-efficacy [53]. Furthermore, cooperative learning that offers equal collaboration can create a democratic and harmonious learning environment, fostering equal and trusting relationships between teachers and students. This approach not only stimulates the sense of responsibility of each group member [48], but also generates positive emotions and psychological qualities such as optimism, basic trust, self-confidence, self-reliance, autonomy, a higher sense of self-worth, and tenacity [54]. These qualities lay a solid foundation for future English learning self-efficacy. Thirdly, when displaying results, the teacher provides each student with an opportunity to showcase their talents. If students feel they have grown personally or gained a better understanding of something, they can experience the satisfaction of success, which can improve their self-efficacy [55]. Finally, verbal persuasion relies on suggestions from peers and teachers [56]. Positive and elaborate verbal persuasion can be effective in increasing self-efficacy [57, 58]. During the evaluation phase, group members suggest, encourage, and hint at each other to enhance each other's self-confidence and create an atmosphere for improvement together. Furthermore, the teacher's guidance, motivation, and recommendations can also assist students in obtaining verbal reinforcement and improving self-efficacy by boosting their confidence in their learning abilities.

2.4 Previous study about the impact of flipped classroom on English learning self-efficacy in China

Recent literature shows that studies on the impact of the flipped classroom model on students' self-efficacy in English language learning in China have mainly been conducted in universities. Several researchers have investigated the influence of the flipped classroom model on self-efficacy in English language learning among university students. The results indicate that the model can enhance learners' self-efficacy. According to Wei [59], the flipped classroom approach can enhance learners' self-efficacy by optimizing the classroom learning environment. Wei discusses the impact of the learning environment of the flipped classroom on students' learning self-efficacy, including learning content, learning support, and social structure of learning [59]. Liu and Guan [60] investigated students' English learning self-efficacy in the flipped classroom using questionnaires and an experimental method. They concluded that the flipped classroom promotes independent thinking, fosters a sense of independent learning, enhances motivation and learning efficiency, and enables students to fully utilize their personal strengths [60]. Wang [61] used a quasi-experimental approach to investigate the effect of flipped classrooms on students' English learning. The results showed that students experienced an increased sense of self-efficacy through self-directed learning, classroom discussion, and post-class summarization. They also gained more confidence in their learning, developed a greater interest in the subject, and acquired more knowledge and skills [61]. ** of the flipped classroom. Prior to grou**, teachers must have a comprehensive understanding of their students' learning characteristics, interests, and abilities. This will enable them to make appropriate grou**s based on the actual situation of the students. During the grou** process, teachers should strive to balance the strengths of each group, ensuring that each group has students of varying levels. This will promote mutual support within the group and enhance the overall learning experience. Teachers should clarify the learning objectives for each group to ensure that students understand their tasks and requirements. This can help stimulate students' enthusiasm and initiative. Once groups are formed, teachers should guide students in working together, encouraging communication and discussion among group members, and promoting knowledge sharing and complementarity. During the teaching process, teachers must closely monitor students' learning progress and performance, and make timely adjustments to grou**s based on the actual situation. This ensures the group's vitality and competitiveness.

4.4 Data collection and analysis

For the collection of student questionnaire data, when the formal questionnaire was formed, the researcher edited the online questionnaire through “Questionnaire Star”, which is a professional online questionnaire design platform. After obtaining permission for data collection from the relevant department of this higher vocational college, the researcher identified the group of students who participated in the questionnaire survey and distributed the online questionnaire to these students in their classrooms through QQ, an instant messaging software. Similarly, after the experiment, the researcher distributed the online post-test questionnaire to the students from experimental class through QQ in their classroom. Data from the students' questionnaires were analyzed through SPSS version 26, which consists of analyses of descriptive statistics accompanied by means and standard deviations.

5 Research results of questionnaire survey

5.1 Research results and discussion before the experiment

Before the experiment, the researcher conducted a questionnaire survey and retrieved the English Learning Self-efficacy questionnaires from the control and experimental classes respectively, and the results are shown in Table 2.

Table 2 Results of English learning self-efficacy before the experiment
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According to the statistical results in Table 2, the p-values of students' sense of course adaptation, sense of goal confidence, and sense of course competence in the control class and the experimental class are 0.521, 0.078 and 0.452 respectively, and each value is greater than 0.05, which means there is no significant difference between the control class and the experimental class in all the dimensions of self-efficacy in English language learning before the experiment, and it indicates that there is not much difference between two classes of students in the sense of English learning self-efficacy before the experiment. The mean values of self-efficacy in English learning for both classes ranged from 3.1 to 3.2, showing a moderate level. And the level of the control class is slightly higher than that of the experimental class.

5.2 Research results and discussion after the experiment

After the implementation of the flipped classroom teaching model in the experimental class for one semester, the researcher conducted a questionnaire survey again for the control and experimental classes respectively. The results are shown in Table 3.

Table 3 Results of English learning self-efficacy after the experiment
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According to the statistical results in Table 3, the p-values of the students' sense of course adaptation, sense of goal self-confidence, and sense of course competence in the control class and the experimental class are all 0.000 (p < 0.05), which means there is a significant difference between the experimental class and the control class in all the dimensions of self-efficacy in English language learning after the experiment. According to the mean values in Table 2, the values of each dimension of English learning self-efficacy in the experimental class are all close to 3.7, while the values of each dimension of English learning self-efficacy in the control class are all close to 3.3, which shows that the scores of English learning self-efficacy in the experimental class are significantly higher than that in the control class. It can be seen that the experimental class using the flipped classroom teaching model had better teaching results than the control class using the traditional teaching model.

5.3 Difference in English learning self-efficacy of the control class and experimental class pre- and post-experiment

In this study, a paired-sample t-test was used to identify the differences in the dimensions of English language learning self-efficacy between pre-experiment and post-experiment of the control class and the experimental class. The results are shown in Table 4.

Table 4 Results of English learning self-efficacy in the control class and experimental class
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According to the results in Table 4, the p-values of the control class students' sense of course adaptation, sense of goal confidence, and sense of course competence are 0.429, 0.913, and 1.000 respectively, and they are all greater than 0.05, which means there is no significant difference between pre-experiment and post-experiment of the control class in the dimensions of in English learning self-efficacy. According to the mean difference, it can be seen that there is little change in the dimensions of English learning self-efficacy in the control class before and after the experiment.

In terms of experimental class, the p-values of the experimental class students' sense of course adaptation, goal self-confidence, and course competence are all 0.000 (p < 0.05), which means there is a significant difference between pre-experiment and post-experiment of the experimental class in the dimensions of in English learning self-efficacy. According to the mean difference, the levels of all dimensions of English learning self-efficacy of the experimental class after the experiment are significantly higher than that before the experiment, and they are in the middle to upper level. This indicates that the flipped classroom teaching model has a positive impact on English learning self-efficacy of the students in the experimental class. The data in Table 4 fully indicate that the flipped classroom model is more advantageous than the traditional teaching model in terms of students' self-efficacy in English learning.

6 Results of semi-structured interview

6.1 Interview results from the instructor

After the experiment, the instructor was asked about the performance of students in the experimental class under the flipped learning. She believed that compared to the traditional teacher-centered teaching method, the students in the experimental class showed higher motivation and initiative in pre-study before class. They were able to learn the materials posted in learning platform, actively communicated with other students, and shared their learning experiences. In class, they were more engaged in classroom discussions and interactions. They take initiative to ask questions, express their opinions, and engage in in-depth discussions with other students. This helps them better understand and master the course content, and demonstrate their learning result in class.

When probed about students' performance in group collaboration, the instructor emphasized the importance of group collaboration. She would divide the groups based on students' learning abilities and interests and assign different roles, with each group having clear learning objectives and tasks. As a result, students in the experimental class demonstrated high motivation and initiative in group collaboration. The team members actively listened to each other's viewpoints, expressed their opinions, learned from each other's strengths, and collaborated to solve problems and accomplish tasks. In group work, proficient students can take the initiative to share their learning experiences and skills to help others understand and master relevant knowledge points. Such experience sharing can assist struggling students in finding suitable learning methods and strategies. Students can also help and encourage each other. When students who struggle with learning encounter difficulties, their peers can provide support and encouragement to help them overcome obstacles and boost their self-confidence. Additionally, they can receive feedback and suggestions from their peers to improve their learning methods and attitudes.

The students in the experimental class exhibited a strong sense of teamwork and responsibility in group collaboration. They fulfil their duties and tasks conscientiously, making positive contributions to group learning and discussion. They take the initiative to care for and help other members, fostering a good team atmosphere and cooperative relationships. Students who struggle with learning can enhance their sense of responsibility and participation by taking on certain tasks and responsibilities. This sense of responsibility and engagement can enhance their motivation to learn and prompt them to study harder, thereby improving themselves.

At last, the teacher stated that flipped learning can stimulate students' interest and motivation in learning, improve their self-confidence, independent learning ability, classroom engagement, and self-efficacy. However, it also places higher demands on teachers' activity design. Organizing classroom teaching activities that align with the characteristics of the learning content and encouraging all students to participate in classroom discussions pose significant challenges for teachers. The success of the flipped learning relies on students' ability to learn independently before class. However, some students with low self-motivation and weak foundational knowledge may struggle to keep up with the pace of instruction. Therefore, teachers must provide adequate supervision and counselling after class.

6.2 Interview results from the students

The researcher also conducted an interview with six students from the control class and six students from the experimental class with varying levels of English proficiency. Six students in the control class felt that they were able to acquire clear learning objectives, gradually master knowledge under the guidance of the teacher, and consolidate what they had learned through practice and revision after class. However, they felt that the classroom atmosphere was dull and lacked opportunities for self-exploration and participation. Students with average and weak English foundations in control class expressed less interest and motivation in learning, while those with a good English foundation reported they need to do a lot of preparation after class to keep up with the teacher's pace.

By contrast, six students in the experimental group agreed that the classroom atmosphere was dynamic and that they were more engaged in class. They enjoyed participating in class discussions and group cooperation, as well as exploring knowledge independently through pre-class preview and post-class review. Three students mentioned challenges with the flipped learning. They found that they needed to spend more time and effort on preview before class and be more attentive during class to participate in discussion and activities. However, with the teacher's support and encouragement, as well as help and suggestions from other group members during collaboration, they gradually built up their self-confidence and a sense of responsibility, increased autonomy in learning, had more positive attitudes towards learning, and more effective learning strategies. Moreover, results display enabled them to gain a sense of accomplishment, leading to more optimistic attitudes towards their future performance in the English course.

7 Discussion

According to the results of the pre-experiment questionnaire, there was no significant difference in the dimensions of self-efficacy in English language learning between the experimental and control classes before the experiment. This suggests that the two classes were at a similar level prior to the experiment, providing a basis for comparison of the subsequent results. The results of the post-experiment questionnaire indicated that the experimental class outperformed the control class in terms of their sense of course adaptation, goal confidence, and course competence. This suggests that the flipped classroom teaching model had a positive impact on the English learning self-efficacy of the students in the experimental class.

Furthermore, the pre- and post-experiment comparison of the experimental class revealed a significant increase in students' English learning self-efficacy. This result further supports the effectiveness of the flipped classroom teaching model. However, it should be noted that the control class did not exhibit significant changes before and after the experiment. The reason for this may be that the control group was still using traditional teaching methods and was not exposed to the new teaching approach. This provides further evidence of the benefits of the flipped classroom teaching model in enhancing students' self-efficacy in learning English.

Specifically, the flipped classroom teaching model prioritizes active learning and requires students to prepare before class using video lectures, online courses or other resources. This approach allows students to learn at their own pace and in their preferred style, promoting their learning initiative and autonomy. Active learning and exploration help students to better engage with the course content, enhancing their sense of course adaptation. Additionally, the flipped classroom teaching model typically involves in-class activities such as group discussions, case studies, or project collaboration. These activities offer students more opportunities to interact and collaborate. Through interaction with peers and the instructor, students can share knowledge and experiences, and work together to solve problems. This enhances their sense of goal confidence and course competence. Moreover, the flipped classroom teaching model enables teachers to personalize the learning experience by adapting the teaching methods and content to suit the needs and interests of individual students. This personalized approach enhances students' comprehension and mastery of the course material, boosting their self-confidence and self-efficacy. In the flipped classroom teaching model, teachers can monitor students' progress and receive feedback through classroom interactions, group discussions, and assignments. This allows teachers to adjust their teaching strategies and provide targeted guidance and support based on students' performance and needs. As a result, students can improve their sense of course adaptation, self-confidence in achieving their goals, and course competence.

Based on the interviews of the instructor and students, it was found that flipped learning had a positive impact on the performance of students in the experimental class. These students demonstrated higher motivation and initiative in pre-class preparation and classroom interaction. They were able to attentively study the materials posted on the learning platform, actively communicate with their peers, and participate more in class discussions and interactions. During group collaboration, students in the experimental class demonstrated a strong sense of teamwork and responsibility. They supported and encouraged each other, and shared their learning experiences and skills. Flipped learning is an effective method to stimulate students' interest and motivation in learning. It also enhances their self-confidence, independent learning ability, classroom participation, sense of achievement, and self-efficacy. Meanwhile, flipped learning presents some challenges, such as the requirement for students to invest more time and effort in pre-class preparation and classroom interaction, as well as the increased demands placed on teachers in terms of activity design and supervisory counselling.

8 Conclusion

The results of the questionnaire and interviews showed that students' self-efficacy in English learning is significantly improved through the reform of the flipped classroom teaching model. First of all, students' learning model changed from traditional learning knowledge points in class and completing homework after class to independent learning before class, and students can independently choose the content and form of learning and grasp the learning rhythm suitable for themselves. In the classroom, students can participate actively in group discussions, evaluate their peers, and engage in mutual learning. This fosters a sense of dignity and achievement among students. Secondly, teachers tailor their teaching to students' needs according to their foundation and teaching content, fully mobilize students' internal motivation to learn, guide students to complete their learning tasks, master their learning content, reflect on and summarize their own learning results, and ultimately change their own learning strategies to improve their learning efficiency. Finally, the teacher can also analyze the non-intellectual factors such as self-awareness, autonomy and self-adjustment of students in the process of independent learning through the data provided by the course platform, and assess their motivation, cooperation, reflection, and control in the learning process. Through the flipped classroom teaching model, instructors and students collaboratively construct a dynamic and effective learning environment that nurtures self-efficacy, fosters independent thinking, and encourages active engagement. Ultimately, this leads to more successful learning outcomes.

However, the flipped classroom is not a universal solution for teaching reform. The practices of flipped classroom require collaborative efforts from both instructors and students. Instructors should actively shift their thinking and beliefs, providing effective support and services to students, while creating high-quality classrooms that align with students' developmental characteristics. Similarly, students should elevate their proactive learning abilities, bolster their self-efficacy, and work towards enhancing various skills.