 can say the result shows that different gender has effect on purchase intention. This means that the gender has an impact towards purchase intention of Smartphone among office staff in the North of Vietnam. Hypothesis:  H0: There is no impact from age towards purchase intention of Smartphone among office staff in the North of Vietnam.  H1: There is an impact from age towards purchase intention of Smartphone among office staff in the North of Vietnam. Table 13 one-way ANOVA shows that the sig value is 0.033. This value is less than 0.05. Because of this, we can conclude that there is a statistically significant difference between the age variable and purchase intention variable. There is an influence between the ages of customer with purchase intention of customer, different age has affected on purchase intention. It means that the young people have trend buy Smartphone more than old people. There are some reasons can explain for that:  The young people want to express themselves  They want to become a modern people  They want to follow their hobby and the modern technology Hypothesis:  H0: There is no impact from marital status towards purchase intention of Smartphone among office staff in the North of Vietnam.  H1: There is an impact from marital status towards purchase intention of Smartphone among office staff in the North of Vietnam.
Look at the Sig value of Table 14, we have the significant value is 0.045, it is less than 0.05. We can conduct that there was a significant difference between marital status and purchase intention and it means that different marital status has effected on purchase intention. The table shown that the number of single person took part in responded the questionnaire survey is more than the number of married person. Marital status affects to purchase intentions because of some follow reasons:  The single person has much free time to find research and follow their hobby.  The single person does not worry about their finance too much.  The married person have to spent time for their family don't have much free time to find, research about the Smartphone  They have to spent money reasonably Hypothesis:  H0: There is no impact from income towards purchase intention of Smartphone among office staff in the North of Vietnam.  H1: There is an impact from income towards purchase intention of Smartphone among office staff in the North of Vietnam. Table 15 shows that among different group of income, significant level is 0.12 which is lower than α = 0.05, we accept H1. It means that there is an impact from income towards purchase intention of Smartphone among office staff in the North of Vietnam.

Summary
Through the survey conducted, there are four main factors affecting Smartphone purchase intention of office staff in the North of Vietnam. They are:  Price factor  Brand factor  Design factor  Feature factor The above factors are very important for the businesses or Smartphone manufactures to have proper strategies and actions to produce and give Smartphone that suitable with office staff and consumers in many aspects. Moreover, it helps the businesses can meet customer expectations in order to gain market share in Vietnam over its competitors.
In this research, we test the reliability through Cronbach's Alpha system and factor analysis EFA. The result shows that all of factors have Crobach's Alpha > 0.6 so they meet requirement and have high reliability. Therefore, these scales will be used to analysis.
ANOVA test by the author has showed that different groups of gender, significant level is 0.044; among different group of age, significant level is 0.033; among different group of marital status, significant level is 0.045; among different group of income, significant level is 0.012 which are all less than alpha 0.05 which means that there is different by group of gender, age, marital status, income which has affected purchase intention.

Conclusion
When social develops, technology also develops, it is development of Smartphone, and it becomes a part very useful and indispensable in our life. It can replace computer or laptop and it is very convenient. Nowadays, many people seem Smartphone is tool in working or relax. The demand of Smartphone increase very fast and it became a common need of every people so the Smartphone market is a potential market and the business need to invest.
The aim of this study is to find out the elements affecting Smartphone purchase intention of office staff in the North of Vietnam. Some influencing elements that affect office staff purchase intention are price, brand, design, quality, and feature. After knowing the elements affect purchase intention, the next purpose of this study is to understand what elements will affect purchase intention of office staff. Based on the survey result that we collected in the North of Vietnam, we knew that great of the office staff use Smartphone in working and relax.
By using descriptive analysis we had an overview of the demographic statistics and based on the respondent's replies, the mostly the number using Smartphone of office staff in the North of Vietnam is male with 64%, there were more single consumers than married consumers, and it took 56%. It means that the single people do not worry about money to buy something for their family than married people. Based on respondent's age result, the great number of consumers using Smartphone is in-group from 22 to 30 years old, it up to 47%. Office staffs with a month income from 3.000.000 to 4.000.000 VND is largest with 45%.
To test the reliability, we used Cronbach's alpha system and factor analysis. The result shown in Table 8 indicated KMO is 0.731>0.5 and significant is lower than 0.01 and therefore factor analysis is appropriate.
We used ANOVA test to know different group gender, age, marital status, and income affect or do not affect purchase intention. And the result shown that among different group of gender significant level is 0.044; among different group of age significant level is 0.033; among different group of marital status significant is 0.045; among different group of income level is 0.012 which are all lower than 0.05. It means that different gender, age, marital status, income have affected purchase intention.
In conclusion, the research found main elements affect Smartphone purchase intention are price, brand, design and feature. The businesses or Smartphone manufactures can base on this research to emphasize those elements to attract more office staff, more other consumers and develop the Smartphone industry in Vietnam. The business should give some strategies and some solutions such as:  Low price  Famous brand  Design with eye-catching  Unique feature

Research implication
Based on the information gathered from the research on elements affecting Smartphone purchase intention of office staff in the North of Vietnam, this study provides some implications may be useful for the business and manufactures want to increase the demand of Smartphone among office staff target market. Nowadays, the office staff and other consumers want a Smartphone with famous brand, lower price, and good design and so on. It helps the business, manufactures to make further improvements, and used marketing strategies to increase the sales of Smartphone. According to the result of the research, Price has the highest significant affecting Smartphone purchase intention of office staff in the North of Vietnam. So, the businesses and manufactures are suggested to increase the office staff's purchase intention by the ways such low price. In addition, the businesses can base on the research to give famous Smartphone brand. It is an important thing because there are many the consumers think that famous brand brings to more high quality products or it shows that they will feel confident when they have a famous Smartphone brand.
Based in the research done, Design has the significantly impact on purchase intention of Smartphone among office staff in the North of Vietnam. Therefore, Smartphone companies can focus on the design of Smartphone such as the size, shape, button placement, color, and other decorative. They are the first thing that many consumers use to make a snap decision right away, on whether they buy or do not buy. Moreover, the color of the Smartphone is very important because the female always attend to its.
According to the research done, Features of Smartphone has the significantly impact on the purchase intention of Smartphone among office staff in the North of Vietnam. It is necessary if the manufactures expand Smartphone office software, it can helps office staff in working many work such as word processing, sent and receipt email, finding information. There is an important factor that manufactures need improve is increase the battery life of the Smartphone because the office staffs have many work need to do in one day.

Research limitation
There are some limitations in this study. Firstly, the result may not be comprehended for the businesses because the samples only collect on one area and one subject of Vietnam which is in the North of Vietnam with subject is only office staff. It cannot stand for whole population in Vietnam.
Secondly, there are only five independent variables in this study and there might have other factors, which did not take in to. Those factors that were not included in this study may be the influential forecasters of purchase intention of Smartphone among office staff in the North of Vietnam. In addition, there is a limitation for the study is only used of survey questionnaire because some below reasons:  It may be lack validity  The respondents may not be understand the question and they can randomly select an answer to complete the questionnaire  The respondents do not spent much time and effort in completing the survey.  There are many responses from the respondents because different people would have different views based on their understandings.  All of these could reduce the accuracy and preciseness of the results and it makes the research will be untrustworthy.question: