William Olsten, who founded a temporary-help business and helped create an industry, died Sunday at his home in Old Westbury, N.Y. He was 72. Mr. Olsten opened his first shop in 1950 at a time of increasing demand for women to do office work. As the company grew, so did the need for temporary help, and an industry was born. The company later broadened to include new categories such as technical personnel, professional services, data and word processing and staff leasing. Westbury, Long Island-based Olsten has more than 700 offices in North America and is the third-largest company in the temporary service industry. Mr. Olsten grew up in Yonkers and attended New York University's School of Commerce, graduating in 1951.