The stock market showed a small loss today as traders studied the latest data on economic growth. The Dow Jones average of 30 industrials dropped 3.32 to 2,852.94 by noontime on Wall Street. Losers outnumbered gainers by about 8 to 7 in nationwide trading of New York Stock Exchange-listed issues, with 618 up, 695 down and 551 unchanged. As the business day began the Commerce Department reported that the gross national product grew at a 1.3 percent annual rate, after adjustment for inflation, in the first quarter of the year. The reduction in the figure, from a previous estimate of 2.1 percent, was larger than most analysts had been estimating. But the significance of the numbers was clouded by word that the difference stemmed to a great extent from a downward revision of business inventories rather than final sales. A shrinkage in inventories can be interpreted not as a clear sign of economic weakness, but rather as a possible portent of an approaching pickup in production demand. Interest rates were unchanged to narrowly lower in the credit markets following the news. Philip Morris led the active list, down 1&rsqb; at 43}. Brokers cited a federal regulator's push to ban cigarette vending machines, and news that the City University of New York and Harvard University had decided to sell their tobacco stocks. U.S. Shoe, which reported sharply higher quarterly earnings, climbed 1&rsqb; to 24~. The NYSE's composite index of all its listed common stocks lost .26 to 195.59. At the American Stock Exchange, the market value index was up .72 at 360.37. Volume on the Big Board came to 71.45 million shares at noontime, against 83.65 million at the same point Wednesday.