March 29, 1982

''I think we have to do it to demonstrate something to the whole world.'' - Oscar Gonzalez, voting in El Salvador. (A1:6.)

A headline on Sunday incorrectly stated the rate at which medical costs in the United States are climbing. The nation's health-care bill has climbed tenfold in the last two decades, from $27 billion in 1960 to $275 billion last year.

Coleco Industries, a leading maker of games and toys, was the best performing stock on the New York Stock Exchange in the first quarter, rising 96.4 percent. The Texas International Company, an oil and gas exploration concern, turned in the poorest showing, dropping 65.7 percent. A list of the best and worst performers on the Big Board, the American Stock Exchange and the over-the-counter markets is on page D4.

In the Great Tin Mystery - a $500 million business who-done-it - the clues all lead to Kuala Lumpur, the capital of the world's largest tin producer. Malaysia has neither confirmed that it was the kingpin in the plot to corner tin, nor denied that its warehouses are full of the key metal. But those who follow the trading of tin have no doubt that Malaysia was involved. Seen from Malaysia's point of view, the bizarre actions of the past eight months do make sense. Malaysia did, and still does, have a lot to gain from the uncertainty that grips the world tin market.

The Legislature is about to pass what some view as a spend-now, pay-later budget. News analysis, page B3. By JOYCE PURNICK Mayor Koch yesterday criticized as ''counterproductive'' an agreement by the leadership of the State Legislature that would delay some financing for the Westway project. ''This project cannot be stopped,'' he declared. ''It will ultimately be built.''