NEW YORK - Investors are trying to get a read on the economy using earnings reports. They're finding it's not so easy.

The result Tuesday was yet another erratic day of stock trading. The Dow Jones industrial average rose 75 points after having fallen 140 in early trading in response to a series of disappointing revenue reports. Analysts were hard-pressed to come up with a reason for the turnaround. But trading was extremely light, and that tends to skew stock prices.

Analysts said some investors were getting a little more upbeat as they awaited earnings reports from Yahoo Inc. and Apple Inc. after the close. But those reports came in mixed, just like those from the many companies that have also reported second-quarter results. Apple's stock surged in after-hours trading, but Yahoo fell. Like IBM Corp., Johnson & Johnson and Goldman Sachs Inc., its revenue fell short of expectations.

Investors have been quick to sell on even a whiff of bad news. Early Tuesday, they were motivated by the reports from IBM, J&J and Goldman. Investors have been focusing on revenue rather than bottom-line earnings because of the link between companies' sales and the economy. If revenue is down because consumers aren't spending, that's a sign that the economy could remain weak.

Investors seem to have decided as Tuesday wore on that earnings didn't look quite as bad as they first thought. Analysts noted that Goldman's drop in revenue was similar to those reported by JPMorgan Chase & Co., Citigroup Inc. and Bank of America Corp. Their revenue fell not because of a weak economy, but because their customers decided to avoid the financial markets' turbulence during the spring.

Some analysts said there were technical factors involved in the market's moves.

"Investors may have been anticipating the market heading back to early July lows so when it didn't fall apart in early trading, they slowly came back in," said Michael Sheldon, chief market strategist at RDM Financial Group in Westport, Conn.

Those investors were looking at charts that track the movements of indicators including the Standard & Poor's 500. When the S&P reaches, or doesn't reach, a specific level, that can prompt investors to buy or sell.

It was hard to predict what turn trading might take Wednesday. Yahoo and Apple are considered indicators of the overall economy, but their mixed results weren't giving investors a clear-cut direction for stocks.

According to preliminary calculations, the Dow rose 75.53, or 0.7 percent, to 10,229.96. The broader Standard & Poor's 500 index rose 12.23, or 1.1 percent, to 1,083.48 and the Nasdaq composite index rose 24.26, or 1.1 percent, to 2,222.49.

Advancing stocks were ahead of losers by 4 to 1 on the NYSE, where volume came to an extremely light 1.1 biillion shares.