INVESTIGATIONS OF CUSTOMER LOYALTY: STRENGTHENING PRODUCT QUALITY, BRAND IMAGE AND CUSTOMER SATISFACTION

The purpose of this study is to increase customer loyalty through improving product quality, brand image and customer satisfaction. The population of this study were 27,378 students in Karawang from 12 universities. The sampling technique used was stratified random sampling, with a total of 550 participants. Data analysis was performed using statistical analysis Structural Equation Model (SEM) using Amos Graphic software version 22. The results obtained that the increase in product quality has a direct effect on customer loyalty, brand image and customer satisfaction is a mediator of product quality factors on the loyalty factor. customer. The implication of this research is that brand image is the biggest factor affecting customer satisfaction. Furthermore, the contribution from this research results for OPPO’s company is to consider about their management policy to improve their product quality through technological innovation in terms of using high-quality materials, features, and components to improve brand image, customer satisfaction so that it has a positive impact on customer loyalty


INTRODUCTION
Public demand for service quality in the era of globalization is very urgent, therefore, companies must improve their capabilities which oriented towards consumer interests. Competition in market share is needed for the company to be able to survive in producing a product that meet consumer needs and satisfactions. Customer satisfaction is a form of feelings that arise from 79 ISSN : 2088-1231 E-ISSN: 2460-5328 DOI: dx.doi.org/10.22441/mix.2021.v11i1.006 products and services. In this study, he wanted to investigate the consumer loyalty of OPPO products through strengthening product quality, brand image and customer satisfaction. Based on the Top Brand Index measurement of a smartphone product brand, in 2017 the highest Brand Index was: Samsung 46%, Nokia 10,9%, Blackberry 9,8%, iPhone 5,8%, Smartfren 5,4%, Lenovo 4%, OPPO 3,4%, ASUS 3,2% (https://www.topbrand-award.com/top-brand-index/). Therefore, the marketing performance of 3,4% is a big problem for OPPO. The results of the 2017 top brand survey show that OPPO is ranked 2 nd from the bottom after ASUS. Therefore OPPO is required to carry out the research and development of the latest technology to provide the product quality that consumers want (Jindal, 2020). Problems that occur in OPPO product innovations such as the OPPO A7 smartphone is that the product still use micro USB, while competitors such as Samsung and Xiaomi at similar prices have used USB Type C which, is more sophisticated and future proof. In terms of product quality, there are still many assumptions from public that the materials used by OPPO feel cheap compared to competitors such as Samsung which are more solid and rigid, this kind of condition certainly makes the OPPO brand image less attractive for costumers and low customer satisfaction (Rosalina et al, 2019). According Magdalena & Wilzarwan (2019) the problem of low OPPO Smartphone customer loyalty is due to customer expectations that are not fulfilled, product quality that is not competitive, and has no uniqueness so that customers are not satisfied. However, there was an increase in OPPO's market share in 2018 to 18% and in 2019 it reached 21.5%. The increase in market share was due to the company continuing to improve its technological innovations so as to increase competition. This phenomenon makes researchers interested in knowing which variables are more dominant in increasing customer loyalty, whether product quality, brand image, or customer satisfaction. The contribution of from this research results for OPPO"s company is to consider about their management policy to improve their product quality through technological innovation in terms of using high-quality materials, features and components to improve brand image, customer satisfaction so that it has a positive impact on customer loyalty. This research participants involved students in Karawang. According to PDDIKTI (2019) there are 11 private universities and 1 state university in Karawang, with a total of 27,378 students as a population consisting of 13,000 public and 14,378 private students.
Product Quality. Product quality is the ability of a product to show its performance including durability, reliability, ease of operation, fresh design, high capacity memory, long battery life and features in accordance with user wishes (Cheng-Ping Li, 2017). The quality of the products own by the company encourages customers to make repeat purchases that are more than one time purchase and will recommend to friends or family (Hanim & Nurjanah, 2019). Product quality is the advantage of the total of features and characteristics of a product or service that depend on its ability to meet customer needs. The performance and the feature dimension are used for competitive advantage marketing strategies. Performance refreshes to main operating characteristics/function of product, while the feature dimension refers to additional characteristics to increase product attractiveness for customers (Chen Hoe & Mansori, 2018). Product quality has a direct influence on customer loyalty (Lestari & Yulianto, 2018).

Brand Image.
Brand image is consumer confidence in a brand based on the perception of experience and consumer assessment of a product in the market (Yunaida, 2017). Brand image is a set of customer beliefs about a particular brand. Brand image must be managed carefully because it is an important asset for organizations to create corporate value. Dimensions of the brand image include the user image and product image (Wang et al, 2016 (2015) brand image has an influence on customer loyalty. Empirical studies prove that brand image significantly influences customer purchase decision.

Customer Satisfaction.
Customer satisfaction is the level of feeling satisfied or dissatisfied after comparing what consumers have received and expected. Customer satisfaction is also based on the Aftersales service of the product (Asyiah, 2019). Feelings are an accumulation of customer purchasing and consumption experiences (Listyawati, 2018). Satisfaction with a brand has a relationship and even has a significant effect on customer loyalty (Sulibhavi & Shivashankar, 2017).

Customer Loyalty.
Customer loyalty is the willingness of customers to maintain relationships with the company, continue to buy and use product and services as well as tends to recommend to others (Chen Hoe & Mansori, 2018). Customer loyalty to a company brand depends very much on the company"s ability to manage the factors that affect brand loyalty. The results of the study state that there are three factors that shape customer loyalty, namely product quality, brand image and customer satisfaction (Listyawati, 2018). The results of Juhari"s (2018) research state that product perspective, brand image and customer satisfaction affect purchasing decisions.

Research Objectives.
In connection with the issues raised, the main purposes of this study is to help to make decisions about increasing customer loyalty through strengthening product quality, brand image and customer satisfaction.for OPPO"s smartphone brand at College Students in Karawang.
More specific targets from this exploration are: a) To determine whether product quality has a significant influence on customer loyalty for OPPO"s smartphone brand b) To determine whether brand image has a significant influence on customer loyalty for OPPO"s smartphone brand c) To determine whether the product quality factors has a significant influence on the customer satisfaction factors. d) To see the extent to which product quality factors have a significant effect on brand image. e) To examine the effect of mediating customer satisfaction factors on the relationship between product quality factors and customer loyalty. f) To empirically test the mediating effect of product quality on the relationship between brand image factors and customer loyalty.

LITERATURE REVIEW
Customer Loyalty. Factors that influence customer loyalty are product quality, brand image and customer satisfaction (Chen Hoe & Mansori, 2018). Research results from Andrew, M. (2016) showed that brand image and satisfaction had significant direct effect on loyalty, while the results from Anuraga (2015) research stated that product quality had an indirect significant influence through mediating brand image and satisfaction.
The Relationship Between Brand Image and Customer Loyalty. The relationship between product quality and customer satisfaction has direct impact on a customer loyalty (Surya, 2018). Meanwhile, the result of research by Awal, et al (2018)  maintaining a loyal customer base is far more profitable for companies than attracting new customers. So it can be hypothesizedas follow: H1 : Customer satisfaction positively affects on customer loyalty.

The Relationship between Brand Image and Customer Loyalty.
There is a significant relationship between brand image and customer loyalty in the context of retail supermarket chains in the United Kingdom (Neupane, R, 2015). Likewise, Dewi (2017) states that brand image and customer confidence have a significant relationship to customer loyalty. so it can be hypothesized: H2: Brand image positively affects on customer loyalty.
The Relationship between Factors of Product Quality and Brand Image. According to Cheng-Ping Li (2017) product quality is an item offered to the market to get attention as brand image that can satisfy customer needs. Meanwhile, Faizal & Nurjanah stated that there is a direct and significant effect on brand image through product quality indicators such as performance and features and can further increase customer loyalty. So it can be hypothesized: H3: Product quality factor has a direct effect on brand image factor.

The Relationship between Product Quality and Customer Satisfaction.
To increase customer satisfaction the company must try to build product based on the concept of innovation to create value for customers by improving aspects of product quality. (Chen Hoe & Mansori, 2018). The research results from Asyiah (2019) state that there is a relationship between product quality and customer satisfaction, then product quality factors such as performance and features have a direct influence on customer satisfaction. So it can be hypothesized: H4: Product quality factor has positive effect on customer satisfaction factor

Mediation Effects of Brand Image on the Relationship between Product Quality Factors and
Customer Loyalty. According to Moreira et al (2017) brand image mediates between product quality and customer loyalty. While the research findings from Sulibhavi & Shivashankar (2017) there is a significant effect of product quality on customer loyalty with brand image as a mediation so that customers feel confident when repurchasing the product. So it can be hypothesized: H5: Brand Image as mediator the linkage between product quality factor and customer loyalty.

Mediation Effects of Customer Satisfaction on the Relationship between Product Quality
Factors and Customer Loyalty. Customer satisfaction mediates between product quality and customer loyalty (Sitanggang et al, 2019). According to Djumarno et al (2018) customer satisfaction has a mediating effect in the relationship between product quality and customer loyalty because of perceived quality of the product by customers. So it can be hypothesized: H6: Costumer satisfaction as mediator the linkage between product quality factor and customer loyalty.
To examines all hypothesis (H1, H2, H3, H4, H5, H6) for the sake of accomplishing this objective, therefore this study developed the followed framework: Conceptual Model. Structural equation model is used in this study to analyze the influence of product quality factor structure, brand image and customer satisfaction on customer loyalty. Therefore, this flowchart provides testing of causality variables. In accordance with the theory, customer loyalty (L) is the dependent variable, while customer satisfaction (S), brand image (BI) and product quality factor (PQ) are independent variables. In addition, customer satisfaction (S) and brand image (BI) are mediating variables between product quality (PQ) and customer loyalty (L). Customer loyalty is measured by two indicators namely use the product (UP) and Recommended to others (R). Product quality is measured based on performance factors (P) and features (F). Customer satisfaction is measured based on output performance (OP) and After-Sales (AS). Brand image is measured based on indicators user image (UI) and product image (PI). These factors are then described in figure 2. as the Proposed Conceptual Framework as follows:  Measure. All variables were assessed using Likert scale from 1 = strongly disagree to 5 = strongly agree. Customer loyalty variables were measured against 2 exogenous variables namely Using Product (UP) and Recommended (R) (Chen Hoe & Mansori, 2018). Measured by sample item "OPPO products that I use are according to needs" (UP) and "I would recommend to others to use OPPO (R) products. Measurement instruments are first tested based on construct validity aims to measure how far the test items are able to measure what is really going to be measured in accordance with the conceptual definition that has been set. Obtained construct validity value Using Product r = 0.701, Recommended r = 0.699 with reliability (Cronbach's alpha = .811). The Product Quality variable is measured against 2 exogenous variables namely Performance (P) and Feature (F1) (Chen Hoe & Mansori, 2018). Measured by sample item "OPPO product performance as expected" (P) and "The features offered by OPPO products are very interesting to use" (F1). The research instrument was tested based on the construct validity, the value obtained Performance r= 0.707. Feature r= 0.673 with reliability (Cronbach's alpha = .894). Brand Image Variables are measured against 2 exogenous variables namely Product Image (PI) and User Image (UI) (Wang et al, 2016). Measured by sample items, namely "Products issued by OPPO are of good quality and have good durability" (PI) and "People who use or buy OPPO products are people who understand good quality" (UI). The research instrument was tested based on the construct validity, the value obtained Product Image r = 0,712, User Image r = 0,704 with reliability (Cronbach's alpha = .867). Customer Satisfaction variables are measured against 2 exogenous variables namely output performance (OP) and after sales (US). Measured by sample items "work / activity (taking pictures, playing games, multitasking) carried out using OPPO products has better quality than other branded products" (UP) and "OPPO products have fast respond and reliable after-sales service"(AS). The research instrument was tested based on the construct validity, the value obtained output performance r = 0,689, after sales r = 0,666 with reliability (Cronbach's alpha = .858). Test of Assumption.The test of assumption is absolutely necessary before SEM analysis performed. Namely, a normality test and linearity test (Taber, 2017). Normality Test. According to Das (2016) normality is the most fundamental assumption in multivariate analysis that is the form of data distribution on a single matric variable in producing normal distribution. Data has a normal distribution if p value > 0.05 at the level of α = 0.05.   (1) there is a positive and significant relationship between product quality and brand image indicated by the correlation coefficient r = .237 and r = .234 this explains that there is a positive relationship between product variables quality (performance and features) with Brand image variables (user image and product image). The results of this study are still relevant to the research of Anuraga (2015) and Anjani (2017); (2) there is a positive and significant relationship between product quality and customer satisfaction with a correlation coefficient of r = .343 and r = .336. The results of this study prove that there is a significant relationship between product quality on performance indicators and  (2017); (3) there is a positive and significant relationship between customer satisfaction and customer loyalty with a correlation coefficient of r = .275 and r = .274. the results of this study prove that there is a significant relationship between the results of this study according to the research of Listyawati (2018); (4) there is a positive and significant relationship between brand image and customer loyalty with a correlation coefficient of r = .288 and r = .283 this proves that there is a significant relationship between brand image (user image and product image) and customer loyalty (use product and recommended). The results of this study are still in accordance with the research of Yunaida (2017) and Leninkumar (2017).

Generated Structural Model.
Because the p. 0.00 (p-value > 0.01), the research produces a structural model better and more appropriate. Therefore, the explanation will be based on the results of the hypothesis in figure 2.  From the data in table 5. Illustrating customer satisfaction has a significant direct effect on customer loyalty (β = 0.723; C.R = 6.025; p < 0.00), or H1 is accepted. This finding is consistent with the results of the study Chen Hoe & Mansori, (2018) which states that the dimension of customer satisfaction effecting the customer loyalty. Other findings from as Asyiah (2019), state that the variable customer satisfaction is measured through the Output Performance (OP) and After-sales (AS) indicators, while the customer loyalty variable is measured through the Using Product (UP) and Recommended (R) indicators. There is positive relationship between customer satisfaction and customer loyalty. The impact of product quality on the customer satisfaction affects the value of the company in the long run. While the results of research by Khoroni et al (2018) stated that the effect of customer satisfaction on customer loyalty contributed 16,48% so that the total effect of customer satisfaction on customer loyalty contributed 34,12%. Meanwhile, the research results from Asyiah (2019) mention that customer satisfaction affect customer loyalty, the strategy improving product quality through improved performance and features can maintain a higher level of customer satisfaction and customer loyalty Secondly, Brand image has a significant positive effect on customer loyalty (β = 0.123; C.R = 2.323 ; p < 0.005), or H2 is accepted. The results of this study are in line with Neupane (2015); Surya (2018), brand image has a significant influence on customer loyalty, through brand image costumers realize and are interested in making product purchases and even recommend to others, which in the end the company"s profitability becomes optimal. This study found that the overall brand image indicators Product Image (PI) and User Image (UI) have a significant positive effect on customer loyalty. the brand image variable instrument used can provide an overview of Product Image and User Image have an influence on customer loyalty Thirdly, product quality has a positive effect on brand image factor (β = 0.508; C.R = 5.582; p < 0.00), or H3 is accepted, the result of this study are in line with Waluya, et al (2019) states that brand image has a direct positive effect on customer loyalty. Likewise, Juhari (2018) research result state that product quality and brand image have a positive effect on purchasing decisions. The findings in this study are that the indicators of product quality include Performance (P) and feature (F). Based on the instrument developed, the performance indicators in terms of design, software and hardware performance are as follows: high memory capacity, fast charging, long battery life, powerful processor. While instruments for feature indicators include; features that suit the user"s desires such as a camera quality, high security, power saving feature and gesture feature.
Lastly, product quality factor has a major direct effect on customer satisfaction factor (β = 0.757; C.R= 7.901; p < 0.00) or H4 is accepted. This results are still in accordance with Waluya et al (2019) shows that product quality and brand image influence customer satisfaction, product quality and brand image have direct impact on the purchasing decision process. In addition, product quality and brand image influence purchasing decisions, mediated by customer satisfaction. Meanwhile, the results of the research by Listyawati (2018); Lestari & Yulianto (2018) stated that product quality factors have a positive and significant impact on customer satisfaction. The findings in this study indicate that the performance and advance features according to the user"s wishes can increase customer satisfaction.
Customer Satisfaction Mediation and Brand Image on Product Quality and the Customer Loyalty. Furthermore, to examine mediating factors between the customer satisfaction and brand image on product quality and the customer loyalty. The test results will be compared to the direct and indirect effect once inserted product quality factor. Model and standard regression coefficient of the estimate can be seen in figure 4. And table 6 below.  From the test results it can be seen the model support the finding that that brand image factor mediate significantly in the relationship between product quality and customer loyalty (β = .515; C.R = 5.592; p < 0.00). It can be concluded that H5 is accepted. This finding is still in accordance with the research result of Lestari & Yulianto (2018) which states that good product quality has a significant effect on customer loyalty by mediating brand image.Brand image has a positive and significant effect on customer loyalty. When the brand image is good in customer minds, then these customers want to have a longer relationship with the company, because they are sure about the company"s brand image (Awal et al, 2018).
The next finding, the model supports that the customer satisfaction mediates significantly in the relationship between product quality and customer loyalty (β = .697; C.R = 7.462; p < 0.000). It can be concluded that H6 is accepted. This finding is accordance with Liemena (2019); Hanim & Nurjannah (2019) states that product quality and service quality mediated by customer satisfaction have positive impact on customer loyalty. According to table 7. It can be described that product quality has an indirect influence on customer loyalty through brand image (61.0%) and direct influence (62.3%). The findings of this study can be illustrated that product quality such as performance and features can increase customer loyalty after they have a perception of the brand image of the product, thus product quality has an indirect effect through brand image on increasing customer loyalty. This is in accordance with the results of research (Sulibhavi & Shivashankar, 2017;Hanim & Nurjanah, 2019). Stated that brand image contributes to customer loyalty and mediates the relationship between product quality and customer loyalty. .593 According to table 8. It can be described that product quality has an indirect influence on customer loyalty through customer satisfaction (35.5%) and direct influence (59.3%). The findings can be explained that when a product quality is in accordance with customer expectations such as OPPO products that have performance and features that are qualified with the instruments developed. The results is still in accordance with previous research, such as research of Widiaswara (2017) which states that product quality has an indirect effect on customer loyalty through customer satisfaction. Meanwhile Waluya et al (2019) state that product quality, brand image and customer satisfaction have an influence on customer loyalty. Another research finding by Sitanggang, et al., (2019) there are direct and indirect influence of product quality on customer loyalty through customer satisfaction and it can be stated that customer satisfaction is useful as an intervening variable between product quality and customer loyalty. 2. There is a positive effect of brand image on customer loyalty. 3. Product quality factors have a direct effect on brand image. 4. Product quality factors have a positive effect on customer satisfaction. 5. Brand image as a mediator between the factors of product quality and customer loyalty. 6. Customer satisfaction as a mediator of the relationship between product quality factors and customer loyalty.

Contribution & Suggestion.
Based on the research findings, from this research results for OPPO"s company is to consider about their management policy to improve their product quality through technological innovation in terms of the use of high-quality materials, features, and components in order to improve brand image, customer satisfaction so that it has an impact. positive on customer loyalty. Suggestion for decision making are to improve product quality in terms of materials, design, software and hardware performance are as follows: high memory capacity, fast charging, long battery life, powerful processor. While for feature includes features that suit the user"s desires such as a camera quality, high standard security, power saving feature and gesture feature. These suggestions if implemented based on the instruments developed will improve the brand image, customer satisfaction and customer loyalty which ultimately increases the company"s profit.