The Lipper GrowthIndex of 30 mutual funds was 431.58, down 1.32 points, or 0.30 percent, from Thursday. A year ago the index was 503.85.

The index, based on the net asset value of the 30 largest growth mutual funds, was set at 100 in 1968. At the end of 1989, the combined assets of the 30 funds stood at $44.8 billion, according to Lipper Analytical Services Inc.