NEW YORK, May 11 (AP)ÛÓFears of rising interest rates and an apparent new policy of tighter credit by the Federal Reserve Board helped push the stock market lower today.</br></br>The Dow Jones average of 30 industrials was down 9,24 points to 926.00, wiping out TuesdayÛªs moderate gain of 3.05 points. The Dow has recorded a net loss of more than 16 points over the past four sessions.</br></br>Big Board volume was 18.98 million shares, down from the 21,09 million traded the previous day. Nationwide turnover in NYSE-listed issues ÛÓ including trades in those stocks on regional exchanges and in the over-the-counter marketÛÓcame to 22.44 million shares.</br></br>Brokers said the downward trend generally reflected investor concern over the Federal Reserve BoardÛªs apparent move to tighten credit for the third time in two weeks. The Fed hinted at a new policy Tuesday by allowing rates on key Federal funds to rise, then supporting that level.</br></br>There also were fears that hikes in short-term interest rates soon might push the prime rate higher, analysts said.