Many different factors affect the success rate of small businesses, and they tend to vary with the specific business. Success in a franchise, a new restaurant, a mobile app company, or a web design firm are very different.
One common factor in success or failure of a new business is adequate start-up funding. It normally takes at least a year for a new business to become profitable, and so if you start without adequate funds your chance of success will be lower. Many people start a new business as a second job, or as part of a two income family in which their partners supply a regular income. Having substantial experience in the industry and a good client base will also make a difference.