Disappointing earnings reports from the tech giants Amazon and Alphabet set off another turbulent day on Wall Street on Friday, and the benchmark stock-market index briefly dipped into a correction.

Amazon ended down nearly 8 percent and Alphabet, the parent company of the search giant Google, fell 1.8 percent after they reported quarterly results on Thursday evening.

Their reports did little to calm jittery investors who have focused on quarterly corporate updates in search of clues to the economic outlook for 2019. Amazon’s sales forecast for the coming holiday season fell short of investor hopes. And Alphabet’s revenue fell short of analyst expectations.

“The poor earnings are reflecting a slowdown in growth, not a disastrous slowdown, but enough to take stocks down,” said Ilya Feygin, managing director at the institutional brokerage firm WallachBeth.