The influence of celebrity endorsement in social media instagram on attitude towards brand and brand image to customer purchase intention Study on Ayudia Bing Slamet for Rubylicious Brand

Social media Instagram become a platform that give chance for business actors, because Instagram is the most popular social media used in Indonesia. One of fashion industries in Indonesia, Rubylicious, take this opportunity to market the products through social media Instagram. Rubylicious embrace one of influencers in Instagram; Ayudia Bing Slamet as its endorser for Rubylicious brand. This research was conducted to analyze the indicators of celebrity endorsement (credibility, attractiveness, familiarity, & match-up congruence), attitude towards brand, brand image, to purchase intention. The research methodology used for this study is a case study with survey research method. Convenience sampling technique derived from non-probability sampling techniques are used for sample selection. The sample of this research is 175, from people who know the existance of Rubylicious and Ayudia Bing Slamet. Statistical software SPSS and AMOS is used to analyze the data. The research has implications for Rubylicious and other marketers; they can consider some factors needed of celebrity to endorsement strategy. The limitation of this research is some of answers less contributed to explain respondents’ perception clearly.


INTRODUCTION
Social media Instagram became one of the most familiar social medias in Indonesia.Indonesia has topped Asia Pacific's list of Instagram's biggest markets with 45 million active users per month, according to the social media platform's internal data.The number of users more than doubled from the 22 million in early 2016.By the end of 2017's first quarter, Indonesia accounted for over 6 percent of Instagram's 700 million monthly active users (The Jakarta Post, 2017).Related with the use of Instagram as powerful platform for marketers, and the number of Instagram users in Indonesia, it can be opportunity for marketers to promote their products.To get attention of potential customers, marketers use people with thousands followers on their Instagram account, which called celebgram (celebrity instagram).The concept of celebgram is basically come from the concept of celebrity endorsement, who is known by the public for his or her achievements in areas other than that of the product class endorse (Friedman & Friedman, 1979).
To develop previous researches, this research will analyze the effect of celebrity endorsement related attitude towards brand & brand image and the influence to purchase intention on Rubylicious Store.Rubylicious Store utilizes Instagram in every single activity such as posting new collections, giving informations, and also as a media to showing up its celebrity endorser; Ayudia Bing Slamet.Based on interview result with Rubylicious management, one of factors that influence customers attractiveness is by celebrity endorsement, especially for Ayudia Bing Slamet as celebrity endorser proved by increasing followers number on Rubylicious Instagram account and amount of likes on Ayudia photos is bigger compared with noncelebrity photos.This research will analyze the effect of celebrity endorsement characteristics related attitude towards brand & brand image and the influence to purchase intention on Rubylicious through social media Instagram with Ayudia Bing Slamet as its celebrity endorser using four indicators of celebrity (credibility, attractiveness, familiarity, & match-up congruence).

LITERATURE REVIEW AND HYPOTHESES Celebrity Endorsement
Celebrity endorser is an individual who is known by the public for his or her achievements in areas other than that of the product class endorsed (Friedman & Friedman, 1979).Endorsement is a channel of brand communication in which a celebrity acts as the brand's spokesperson and certifies the brand's claim and position by extending his/her personality, popularity, stature in the society or expertise in the field to the brand (Lomboan, 2013).According to Shimp (2007), extensive research has demonstrated that two general attributes, credibility and attractiveness, contribute to an endorser's effectiveness, and that each consists of more distinct subattributes.Miguel (2012) explain, selecting the perfect celebrity to endorse a product or brand is not an easy task.Many researches have been done in order to help on the construction of a guideline model to select the endorser.Some models improved that will discuss in this paper are:

Celebrity Credibility
Credibility is the extent to which the recipient sees the source as having relevant knowledge, skills, or experience and trusts the source to give unbiased, objective information (Belch & Belch, 2008).Ing & Furuoka (2007)

Celebrity Attractiveness
According to Kahle & Homer (1985), Physical attractiveness is an informational cue which involves effects that are subtle, pervasive, and inescapable; produces a definite pattern of verifiable differences; and transcends culture in its effects.According to previous research by Ing & Furuoka (2007), indocators of source attractiveness could be covered by: Classy; Beautiful; Elegant; and Eye-catching.

Celebrity Familiarity
According to Belch and Belch (2001), familiarity is the presumed resemblance as knowledge that a celebrity endorser possesses through exposure.According to previous research by Minh Ha & Hung Lam (2017)

Celebrity Match-Up Congruence
Celebrity matchup principle with product is as important as all other attributes pertains to celebrity for high social acceptability and strengthening the credibility of celebrity (Kotler, 1997).The match-up consists of two central terms: the perceived fit and the image of the celebrity (Hoekman, 2011).Hassan & Jamil (2014), also mentioned two factors in match-up hypothesis, (1) people desire to identify the product with source and so congruity of source with product is much important, (2) people consume those brands which have some association with personalities e.g.relates the brand with own personality, colleagues, fellows, family members or celebrity.

Attitude Towards Brand
Attitude is considered as key concept on consumer behavior that was defined as set of beliefs, experience and feelings forming a predisposition to act in a given direction (Chandon, 2011).According to Sallam & Algammas (2016), attitude is an individual's internal evaluation of an object such as a branded product.An attitude is a permanent, general assessment of people's objects, advertisements or issues (Hoekman, 2011).Attitudes are often considered relatively stable and are enduring predisposition for consumer to behave in particular way (Hoyer and MacInnis in Adyatami & Krisjanti, 2015).

Brand Image
Brand image represents the associations that are activated in memory when people think about a particular brand (Shimp & Andrews, 2013).According to Kotler (2001), brand image also defined as a person's beliefs, ideas, and impression regarding to an object.Brand image is similar to self-image of consumers as consumers associate themselves with brands (Graeff, 1997).The American Marketing Association (AMA) in Mirzai et al. (2016), defines a brand image as: The perception of a brand in the minds of persons.The brand image is a mirror reflection (though perhaps inaccurate) of the brand personality or product being.It is what people believe about a brand their thoughts, feelings, expectations.

Purchase Intention
When intention is someone's desire to do something in the future, Hassan & Jamil (2014) stated purchase intention refers to plan to buy something in future for use but prior to this a cognitive process works behind where several factors consumer perception about product or source person really matters.Purchase intention usually is related to the behavior, perceptions and attitudes of consumers (Mirabi et al., 2015).

METHODS
Type of research is causal quantitative research with survey method using questionnaires for 175 respondents who know the existance of Rubylicious and Ayudia Bing Slamet.The measurement scale used in this study is Likert scale type.The answer of each instrument using Likert scale with 7 scales have gradations from strongly positive to strongly negative.

Full Model Analysis
After analyzing the measurement model through Confirmatory Factor Analysis (CFA) where each variable indicator can be used to prove define latent constructs, then the next step is to conduct a full model SEM analysis with the model result is as follows:  1) Chi-Square and Probability Based on results of SEM analysis is obtained the chi-square value of 528.943 is greater than chi-square table value of 221.438.The chi-square statistic value is accepted in marginal category, because of it produces a probability value of 0.000 is less than α (0.05).Thus, the null hypothesis which states that there is no difference between the population covariance matrix and the sample covariance matrix estimated is accepted.
2) The Minimum Sample of Discrepancy Function with Degree of Freedom (CMIN/DF) Based on the result of SEM analysis is obtained the CMIN/DF value of 2.042 is greater than 2.00.The CMIN/DF value indicated that acceptable fit between model and data, so it can be accepted in a marginal category.
3) Goodness-of-Fit Index (GFI) Based on the SEM analysis result is obtained the GFI value of 0.811 is less than cut of value is 0.90.The GFI value is accepted in marginal category.
4) Adjusted Goodness of Fit Index (AGFI) Based on the result of SEM analysis is obtained the AGFI value of 0.763 is less than cut of value is 0.900.Accordingly, AGFI value is still accepted in marginal category, because the statistic value is greater than 0.6 but it less than 0.9.5) Tucker Lewis Index (TLI) Result of SEM analysis obtained the TLI value of 0.926 is less than cut of value (0.950), so the Tucker Lewis Index (TLI) test can be accepted in marginal category.
6) Comparative Fit Index (CFI) Result of SEM analysis is obtained the CFI value of 0.936 is less than cut of value (0.950), so the Comparative Fit Index (CFI) test can be accepted in marginal category.
7) RMSEA (The Root Mean Square Error of Approximation) Finally, SEM analysis result shows that RMSEA value of 0.077 is less than cut of value of 0.080.Accordingly, the RMSEA value is accepted in a good category.

Hypotheses Testing
Summary results of the critical ratio (CR) values and its value of t table can be seen in Table 1.

First Hypothesis Testing
Based on the confidence level of 95% (α = 0.05) and degree of freedom (n -k) with one tiled test, the t

Second Hypothesis Testing
SEM analysis result shows that the CR value of celebrity attractiveness on attitude towards brand of 2.053 is greater than value of t table .Thus, Ho is rejected and Ha is accepted, it means that celebrity endorser's attractiveness has a positive and significant effect on attitude towards brand.Therefore, second hypothesis which states that celebrity endorser's attractiveness has positive influence on attitude towards brand is accepted.

Third Hypothesis Testing
Refers to the result of Structural Equation Modeling analysis, it is obtianed the CR value of celebrity familiarity on attitude towards brand of 5.094 is greater than t table value.Thus, the Ho is rejected and Ha is accepted, it means that celebrity endorser's familiarity has a positive significantly effect on attitude towards brand.Therefore, third hypothesis which states that celebrity endorser's familiarity has positive influence on attitude towards brand is accepted.

Fourth Hypothesis Testing
Furthermore, based on the SEM result, it is obtianed the CR value of credibility match-up on attitude towards brand of 3.823 is also greater than value of t table .Thus, Ho is rejected and Ha is accepted, it means that celebrity endorser's match-up has a positive and significant effect on attitude towards brand.Therefore, fourth hypothesis which states that celebrity endorser's match-up has positive influence on attitude towards brand is accepted.

Fifth Hypothesis Testing
Based on the result of SEM analysis, it known that CR value of celebrity credibility on brand image of 2.496 is greater than value of t table .Thus, Ho is rejected and Ha is accepted, it means that celebrity endorser's credibility has a positive and significant effect on brand image.Therefore, fifth hypothesis which states that celebrity endorser's credibility has positive influence on brand image is accepted.

Sixth Hypothesis Testing
From SEM analysis result, it known that the CR value of celebrity attractiveness on brand image of 2.388 is greater than value of t table .
Thus, Ho is rejected and Ha is accepted, it means that celebrity endorser's attractiveness has a positive and significant effect on brand image.Therefore, sixth hypothesis which states that celebrity endorser's attractiveness has positive influence on brand image is accepted.

Seventh Hypothesis Testing
Refers to the result of SEM analysis, it can be seen that the CR value of celebrity familiarity on brand image of 3.421 is greater than t table value.Thus, the Ho is rejected and Ha is accepted, it means that celebrity endorser's familiarity has a positive significantly effect on brand image.Therefore, seventh hypothesis which states that celebrity endorser's familiarity has positive influence on brand image is accepted.

Eighth Hypothesis Testing
SEM analysis result shows that CR value of the causal relationship between credibility match-up and brand image of 2.607 is also greater than value of t table .Thus, Ho is rejected and Ha is accepted, it means that celebrity endorser's match-up has a positive and significant effect on brand image.Therefore, eighth hypothesis which states that celebrity endorser's match-up has positive influence on brand image is accepted.

Ninth Hypothesis Testing
SEM analysis result shows that the CR value of attitude towards brand on purchase intention of 4.809 is greater than value of t table .Thus, Ho is rejected and Ha is accepted, it means that attitude towards brand has a positive and significant effect on purchase intention.Therefore, ninth hypothesis which states that attitude towards brand has positive influence on purchase intention is accepted.

Tenth Hypothesis Testing
Based on the result of Structural Equation Modeling (SEM) analysis, it is obtianed the CR value of brand image on purchase intention of 5.803 is greater than t table value.Thus, the Ho is rejected and Ha is accepted, it means that brand image has a positive significantly effect on purchase intention.Therefore, tenth hypothesis which states that brand image has positive influence on purchase intention is accepted.Refers to the limitations of this study, further research need to add the number of respondents, such as ideal number of respondents that proper with the analysis technique in order to obtain results that more accurate.Further research also can extend the studies to incorporate the other independent, mediator or moderator variables like brand credibility and other indicators of celebrity like expertise, and develop wider object to produce the better result, more generally and objectively.Additionally, also can looking for other social medias where celebrity endorsement is exist.The research is suitable not only for fashion product, but also another industry like food and even service industry.

Figure
Figure 1.Research Model

Figure
Figure 2. Full Model SEM

Relationship C.R. t table (one tiled)
hijab in daily life.For the next, Rubylicious may looking for another celebrity who do not wear hijab in order to customer have different role model by celebrity that wears hijab and do not.