Here is where and why most applications fail
Additional Documentation May Be Required
Review the instructions for how to apply for a visa on the website of the embassy or consulate where you will apply. Additional documents may be requested to establish if you are qualified. For example, additional requested documents may include evidence of:
The purpose of your trip;
Your intent to depart the United States after your trip; and/or
Your ability to pay all costs of the trip.
Evidence of your employment and/or your family ties may be sufficient to show the purpose of your trip and your intent to return to your home country. If you cannot cover all the costs for your trip, you may show evidence that another person will cover some or all costs for your trip.
Note: Visa applicants must qualify on the basis of the applicant's residence and ties abroad, rather than assurances from U.S. family and friends. A letter of invitation or Affidavit of Support is not needed to apply for a nonimmigrant tourist visa. If you do choose to bring a letter of invitation or Affidavit of Support to your interview, please remember that it is not one of the factors that we use in determining whether to issue or deny a nonimmigrant tourist visa.
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If the applicant has family in the US, the visa is more likely to be denied. Strong reasons to return to the DR are what they want to see. A job, a long term bank account with steady deposits, family in the DR, a house in the DR, a car in the DR,,, you get the idea.