FACTORS INFLUENCING THE URGE TO BUY IMPULSIVELY OF VIETNAMESE ONLINE BUYING CUSTOMERS TOWARDS BITI’S HUNTER SPORT SHOES

Our study investigates the factors that drive Vietnamese online shoppers in Ho Chi Minh City (HCMC) to make impulsive purchases of Biti's Hunter sports shoes (BHS), using the Stimulus-Organism-Response (S-O-R) theory and the Technology Acceptance Model (TAM). Mixed methods are applied: in-depth interviews with ten regular online shoppers and focus group discussions with e-commerce managers for qualitative data collection, and survey techniques to gather quantitative data from 319 online shoppers. Data analysis was performed using SPSS 22.0 and AMOS 22.0. Our findings reveal five factors as a stimulus - visual appeal, website ease of use, product availability, portability, and social influence – and three factors as an organism - instant gratification, impulsiveness, and trust, that lead to the response of urge to buy impulsively. Significant positive effects are found among these constructs, except the relationship between portability and impulsiveness, visual appeal, social influence, trust, instant gratification, and urge to buy impulsively.


INTRODUCTION
With the proliferation of network technologies, consumers' buying practices are continually evolving.Currently, the vast majority of the consumer market is dominated by online shopping.E-commerce in Vietnam is growing rapidly, especially after almost two years of the COVID-19 pandemic, which shifted most consumers from direct to online shopping.According to a report by Google et al. (2022), consumers buying goods online in Vietnam accounted for 49% of purchases, just behind Singapore (53%) and higher than Malaysia and Indonesia.Therefore, investigation of online customer behavior is necessary to keep up with the development of the market.
Impulse buying is making a purchase without planning, which means that what people actually do when they shop online does not match what they had planned.Previous typical studies investigated online impulse buying that applied many different theories.Liu et al. (2013) studied website attributes in urging online impulse purchases.Marketing knowledge was applied to information systems to explain how website cues affect personality traits to urge impulse purchases online.Additionally, the investigation of Verhagen and Van Dolen (2011) applied cognitive emotion theory to provide insight into the relationships between online store beliefs and consumer online impulse buying behavior.Moreover, Zheng et al. (2019) applied the S-O-R paradigm to examine impulse buying based on situational factors and reaction factors in mobile commerce.However, there is no comprehensive study using both theories of S-O-R and TAM to explain impulse buying, especially in Vietnam.Therefore, it is necessary to study impulse buying behavior in Vietnam by applying both theories.
This paper aims to fill the gap in research by identifying the factors that influence the impulsive buying behavior of online customers towards BHS in Ho Chi Minh City, Vietnam.Our research objectives include: (1) identifying the factors that contribute to impulsive buying behavior, (2) measuring the impact of each factor on the urge to buy impulsively, and (3) proposing solutions to increase Biti's revenue and market share.We applied the S-O-R theory and the TAM to study impulsive buying behavior.The results of this study provide valuable insights into the factors affecting the urge to buy impulsively among online customers for BHS.This information will help online businesses understand their customers' shopping behavior and formulate effective business strategies to attract more customers and achieve better outcomes.

Theoretical background and hypotheses development
The S-O-R model was originally proposed by Mehrabian and Russell (1974) in environmental psychology to explain how environmental factors influence human behavior.In recent years, the S-O-R paradigm has been widely adopted in online consumer behavior studies to explore how human-computer interactions lead to behavioral intentions (Zhang & Benyoucef, 2016).Therefore, it is highly appropriate to use this model in the context of online commerce.
The TAM is a useful tool for understanding the factors that drive impulsive buying behavior online, such as perceived ease of use and perceived usefulness when accessing online shopping websites or applications (Davis, 1989).The factor of ease of use is included in this study's research model based on the TAM.This is because, when it comes to impulsive buying behavior, people are often attracted to the ease and convenience of using technology devices such as mobile phones.
Visual appeal includes fonts, images, and other visual elements that enhance a website's appearance (Parboteeah et al., 2009).Perceived visual appeal directly affects impulse purchases, mediated by user satisfaction and website quality (Loiacono et al., 2007;Wells et al., 2011).A website with visual appeal can increase the instant gratification of online purchases (Liu et al., 2013).Moreover, in the research of Zhao et al. (2022), the investigation presents that visual appeal is positively related to online impulse buying.Visually appealing websites attract customers and evoke positive emotions (Chen, Ku, & Yeh, 2019), and it is assumed that online buying customers are more likely to trust websites with attractive visual appeal.We therefore propose the following hypotheses: H1a: Visual appeal positively affects the instant gratification of Vietnamese online buying customers towards BHS.
H1b: Visual appeal positively affects the impulsiveness of Vietnamese online buying customers towards BHS.
H1c: Visual appeal positively affects the trust of Vietnamese online buying customers towards BHS.
Perceived website ease of use relates to online retail navigation (Verhagen & Van Dolen, 2011).
Easy-to-use websites can boost good feelings and increase impulse purchases (Liu et al., 2013;Verhagen & Van Dolen, 2011).Hence, if a consumer has trouble surfing a site, they are less likely to be satisfied with their purchase.It is assumed that when the website is easy to access and use, a user will be more likely to get a sense of gratification.In the research of Bressolles et al. (2007), it was found that the ease of use of electronic service quality can increase the impulse buying of the customer.Previous studies also have illustrated the effect of website ease of use on online buying impulsively (Liu et al., 2013;Zhao et al., 2022).In addition, website ease of use and trust can increase the satisfaction of mobile users (Amin et al., 2014), leading to an increase in response to the urge to buy impulsively.Thus, we hypothesize: H2a: Website ease of use positively affects instant gratification of Vietnamese online buying customers towards BHS.
H2b: Website ease of use positively affects the impulsiveness of Vietnamese online buying customers towards BHS.
H2c: Website ease of use positively affects the trust of Vietnamese online buying customers towards BHS.
Perceived product availability is related to the online store's variety of products to satisfy potential customers' shopping interests.If consumers cannot find what they want, they will be frustrated and less likely to buy (Chen-Yu & Seock, 2002;Theodoridis & Chatzipanagiotou, 2009).Moreover, product availability is the most important criterion for impulsive clothing buyers (Chen-Yu & Seock, 2002).Yoo el al. (1998) found that consumers like stores with a wide product selection.Theodoridis and Chatzipanagiotou (2009) found that a large assortment affects consumers' store image and satisfaction.This shows that product availability is an important factor affecting impulse buying behavior.As a result, we hypothesize: H3a: Visual appeal positively affects the instant gratification of Vietnamese online buying customers towards BHS.
H3b: Product availability positively affects the impulsiveness of Vietnamese online-buying customers towards BHS.
H3c: Visual appeal positively affects the trust of Vietnamese online buying customers towards BHS.
Portability can be stated as "users can access the internet via mobile devices anytime and anywhere, subject to signal rereception" (Ghose & Han, 2011, p. 1671).Online shoppers using smartphones value portability (Okazaki & Mendez, 2013).Users may access websites on their mobile devices anytime, anyplace, which might considerably boost their surfing time.A previous study by Zheng et al. (2019) found that portability is the environmental stimulus factor that can influence organisms of online buying customers, and this leads to the urge to buy behavior impulsively.This leads to the following hypotheses: H4a: Portability positively affects the instant gratification of Vietnamese online buying customers towards BHS.
H4b: Portability positively affects the impulsiveness of Vietnamese online buying customers towards BHS.
H4c: Portability positively affects the trust of Vietnamese online buying customers towards BHS.
Social influence has been studied based on the theory of TAM, and the results of those studies have indicated that social influences positively influence the technology acceptance of individuals (Venkatesh & Morris, 2000).Research by Slade et al. (2015) proved that social influences have a positive impact on online impulse buying behavior in e-commerce.We assumed that when customers are affected by social influence, they are likely to purchase online impulsively, and therefore hypothesize: H5a: Social influence positively affects the instant gratification of Vietnamese online buying customers towards BHS.
H5b: Social influence positively affects the impulsiveness of Vietnamese online-buying customers towards BHS.
H5c: Social influence positively affects the trust of Vietnamese online-buying customers towards BHS.
Instant gratification refers to the degree of instant gratification a person receives from making an impulse purchase (Liu et al., 2013).Marketing knowledge suggests that, in stores, some consumers can immediately feel gratification after making an impulse purchase (Rook Dennis W & Gardner Meryl P, 1993).Youn and Faber (2000) noted that impulse consumers act quickly and seek instant gratification.Beatty and Ferrell (1998) pointed out that some shoppers who get more gratification from shopping will enjoy shopping more than others.Based on the above discussion, we hypothesize: H6: Instant gratification positively affects the urge to buy impulsively Vietnamese online buying customers towards BHS.
Impulsiveness is defined as "both the tendencies (1) to experience spontaneous and sudden urges to make immediate purchases and (2) to act on these felt urges with little (conscious) deliberation or evaluation of consequence" (Beatty & Ferrell, 1998, p. 174).This construct, which has been examined in both online and offline contexts (Wells et al., 2011), is a significant predictor of impulse purchases.The urge to buy impulsively refers to "the state of desire experienced upon encountering an object in the environment" (Beatty & Ferrell, 1998, p. 172).Several studies have indicated that the construct is an accurate, appropriate, and effective proxy for impulse purchasing.(Beatty & Ferrell, 1998;Liu et al., 2013;Wells et al., 2011).Therefore, we hypothesize that: H7: Impulsiveness positively affects the urge to buy impulsively of Vietnamese online buying customers towards BHS.
Trust is a governance mechanism in exchange relationships that are characterized by uncertainty, vulnerability, and dependence.Developmentally, relationships between parties who have never met should start with small activities that demand little trust.In ecommerce, information security, confidentiality, and trust related to customers are crucial factors to the success of e-commerce services (Eid, 2011;Yi & Jai, 2020).Therefore, to do business successfully on the e-commerce platform requires businesses to create a connection with consumers and gradually strengthen their trust in the product or service that the business provides (Quinton & Harridge-march, 2006;Verhagen & Van Dolen, 2011).The urge to buy is formed by positive feelings (Flight et al., 2012) , and the trust of customers has a significant effect on consumers' positive emotions, which in turn, influences consumers' impulse buying behavior (Yi & Jai, 2020).Hypothesis 8 follows: H8: Trust positively affects the urge to buy impulsively of Vietnamese online buying customers towards BHS.The study uses a mixed-methods design.The qualitative methods used in-depth interviews of 10 regular online-buying customers to explore factors influencing the urge of online buying customers to buy impulsively BHS shoes in HCMC, Vietnam.The focus group discussion with online commerce managers then is applied to explore factors, model modification, and measurement scale.The quantitative methods used a survey technique with a sample size of 319 online-buying customers.The questionnaire was created using measurement scales from prior studies.A five-point Likert scale ranging from strongly disagree (1) to strongly agree (5) was used to measure each item.The three items of the portability construct were adapted from Okazaki and Mendez (2013) and Zheng et al. (2019).Three items from the website ease of use construct were adapted from the measurements of Bressolles et al. (2007), Verhagen andVan Dolen (2011), andLiu et al. (2013).The measurement for visual appeal was developed based on the research of Loiacono et al. (2007) and Wells et al. (2011).The measurement for product availability was adapted from Verhagen and Van Dolen (2011) and Liu et al. (2013).Three items of social influence construct were adapted from Slade et al. (2015), and Venkatesh (2012).The impulsiveness construct measurement was adopted from Rook and Fisher (1995), Parboteeah et al. (2009), andLiu et al. (2013).Three items of trust construct were adapted from Corbitt et al. (2003).Three items of instant gratification were measured based on the research of Rook (1987), Rook Dennis and Gardner Meryl (1993), and Liu et al. (2013).The urge to buy impulsively measurement was adopted from Liu et al. (2013) and Zheng et al. (2019).

Data collection and sample
The data were collected from HCMC, Vietnam, from June to November 2022.Because young customers may be more familiar with and find easier to use mobile devices and modern technology, the respondents were online buying customers from 18-30 years old.According to Hair et al. (2013), the sample size (n) should be 300-384 respondents when the population is higher than one million or/and the population is unknown (with 95% confidence level and a 5% error).
After screening and removing unsatisfactory responses, the number of retained responses was 319.
The descriptive statistical analysis of the sample is illustrated as follows.In particular, 60% of respondents are female, and 40% are male.In terms of age distribution, the proportions are 29.3% and 70.7%, respectively, for 18-25-yearolds and 26-30-year-olds.The primary marital statuses are married (47%), single (35%), and in a relationship (18%).Respondents who are office staff accounted for the highest percentage (37%), followed by those of lecturers (29%), students (30%), and housewives (4%).For personal income per month, the two highest positions are more than 15 million VND (43%) and from 10 million VND to 15 million VND (37%).

RESULT Assessment of measurement model
Cronbach's alpha is the coefficient when assessing the reliability of multivariate scales when the number of observed variables is from 3 or more.Cronbach's Alpha coefficient values (α >0.7) were applied for each factor to assess the questionnaire's internal consistency or reliability (Hair et al., 2013).This study shows all constructs with Cronbach's alpha are greater than 0.7.As a result, all items were acceptable and statistically significant (see Table 1).Moreover, all items of the nine constructs have coefficients of corrected item-total correlation, which are larger than 0.3; thus, there are no items excluded from the scale (see Table 1).

Exploratory factor analysis (EFA)
Exploratory factor analysis (EFA) was applied to identify and confirm the factors under each construct.Variables with factor loading <0.5 will be removed from the scale.This does not meet the requirements of the scale value.According to Hair et al. (2013), the factor loading coefficients are the criteria that help to ensure the significance level of EFA (with factor loading > 0.5 at the minimum level).The results of the EFA analysis show that the total variance extracted from the factors is 78.547 % (>50%), and the value of the factor loading coefficient of observed variables meets the requirements (>0.5) (see Table 1).Moreover, the Kaiser-Meyer-Olkin (KMO) measure of sampling adequacy has a value of 0.843, while Bartlett's test of Sphericity is significant (Sig=.000),indicating that the data is suitable for factor analysis.

Confirmatory factor analysis (CFA)
According to the results of the CFA analysis, the CMIN/DF value = 1.436 (<3), and the TLI and CFI >0.9.In addition, the GFI reached 0.917 (>0.8), the RMSEA was 0.037 < 0.08, and the sig test value of the model was 0.000 < 0.05.Therefore, we can conclude that, at the 95% confidence level, the model is appropriate for CFA analysis, and the data were compatible with the research model.Moreover, the composite reliability (CR) of each factor is greater than 0.7, and the variance extracted (AVE) is higher than 0.5.Both CR and AVE meet the requirement with the suggested criteria of 0.7 and 0.5 (Hair et al., 2013).

DISCUSSION
The study contributes new insights to understanding the determinants of the online urge to buy impulsively.The results indicate that five stimuli factors are visual appeal, website ease of use, product availability, portability, and social influence.These stimulus factors lead to the response of the urge to buy impulsively through instant gratification, impulsiveness, and trust (organism).
With the organism of instant gratification, in line with the hypothesis, the findings show that all five stimulus factors have positive effects on instant gratification.Visual appeal, website ease of use, and product availability are the three factors most influencing instant gratification (H1a: β =0.265 p<0.0001,H2a: β =0.278 p<0.0001,H3a: β =0.224 p=0.05).In other words, when customers feel that the online stores have available products to provide, websites with pleasing displays, attractive layouts of websites, and websites of these stores have relevant and obvious and easy-to-find information about BHS shoes, customers will have more gratification of making a purchase online, leading to the result of a stronger feeling of being urged to buy impulsively.The findings are the same for the organism of impulsiveness.Four stimulus factors out of five have positive effects on impulsiveness (H1b: β =0.258 p<0.0001,H2b: β =0.316 p<0.0001,H3b: β =0.480 p<0.0001,H5b: β =0.192 p=0.026<0.05),and visual appeal, website ease of use, products availability are the strongest stimulus factors for impulsiveness.The portability factor did not affect impulsiveness (H4b: p=0.073>0.05),which can be explained by saying that customers who purchase online BHS were not affected by portability at the moment of making impulsive buying.This finding is also consistent with previous studies by Zheng et al. (2019).For the organism of trust, the finding shows that website ease of use, products availability, and portability have a positive effect on trust (H2c: β =0.272 p<0.0001,H3c: β =0.353 p<0.0001,H4c: β =0.265 p=0.006<0.01).We did not find any significant effects for the relationship between visual appeal, social influence factor, and trust (H1c: p=0.057>0.05,H5c: p=0.166>0.05),.
For testing the relationship between instant gratification, impulsiveness, and trust, the study has significant findings.Instant gratification did not affect the urge to buy impulsively (H6: p=0.836>0.05),and this finding is not the same as previous studies by Liu et al. (2013).However, impulsiveness has positive effects on the urge to buy impulsively, which is consistent with prior studies (H7: β =0.481 p<0.0001).Trust is the new construct that we added to investigate impulse buying behavior in the context of BHS in Vietnam, and this factor has a positive effect on the urge to buy impulsively (H8: β =0.356 p<0.0001).We believe that the research findings can be largely generalizable to other online or offline products.

CONCLUSION AND RECOMMENDATION
Using both the S-O-R theory and the TAM theory, our study explores the factors that influence Vietnamese online customers in HCMC to make impulsive purchases of BHS.The study contributes new insights to understanding the determinants of the online urge to buy impulsively.The finding shows five factors as a stimulus -named visual appeal, website ease of use, products availability, portability, and social influence -and three factors as an organismnamed instant gratification, impulsiveness, and trust -that lead to the response of urge to buy impulsively.Significant positive effects are found among these constructs, except the relationship between portability and impulsiveness; visual appeal, social influence, and trust; instant gratification, and the urge to buy impulsively.These findings update the literature for impulse online buying behavior with the application of both theories of S-O-R and TAM.
Based on this investigation, our study has several implications.We can see that stimulus factors play vital roles in impulse buying.Ecommerce companies can attract more customers by improving the visual appeal of their websites (Wells et al., 2011).Moreover, with easy-to-use features on mobile phones and websites, companies can increase good feelings and portability that lead to impulse purchases (Liu et al., 2013).It also is important to update new products on the website and make sure products are available (Chen-Yu & Seock, 2002).Moreover, businesses that do e-commerce need to connect with their customers and gradually build their trust in the products or services they offer (Quinton & Harridge-march, 2006;Verhagen & Van Dolen, 2011).This study shows the positive effects of social influence.Hence, ecommerce companies can promote advertising on social media because consumer engagement behavior in social media can increase the brand equity of the company (Zailskaite-Jakste & Minelgaite, 2021), which can increase social influence on online buying customers.
We list this study's limitations below.First, this study exclusively examines the shoe company's product.Consequently, future studies might apply the model to additional e-commerce products to confirm this study.The study investigates only in HCMC, which has the most ecommerce enterprises and people in Vietnam.A future study could compare Southeast Asian countries or a developing country like Vietnam to a developed country.Last but not least, personality has a major impact on buying behavior.Thus, we can add extra constructs linked to personality traits to the model to better understand customer behavior.

Figure
Figure 1: Research framework Source: Authors 'work

Table 1 :
Assessment of measurement model