Robert A. Mamis mentioned in "Street Talk" (September) that the Dow average is "capitalization-weighted." This is in error. The Dow average is weighted by the market price of the issues. Percentage moves in high-price issues have more effect on the averages than moves in low-price issues. The New York Stock Exchange and Standard & Poors averages are capitalization or market-value weighted. The formula for the Dow is much simpler than the NYSE or S&P.