US STOCKS-Dow, S&P 500 end up with Merck, IBM; Nasdaq slips with Apple
* Apple shares dip in volatile trading
* Merck has best day since January 2014
* Feb U.S. single-family home prices rise
* Dow up 0.4 pct, S&P up 0.28 pct, Nasdaq down 0.1 pct (Updates to close)
By Caroline Valetkevitch
April 28 (Reuters) - The Dow and S&P 500 ended a volatile session higher on Tuesday, helped by strong earnings from Merck and gains in IBM after it boosted its dividend, while the Nasdaq fell with Apple.
Adding to volatility just before the close, shares of Twitter dropped as much as 24 percent after its results were published early. The stock closed down 18.2 percent at $42.27.
IBM shares rose 1.9 percent to $173.92, giving the Dow its biggest boost. The company hiked its quarterly dividend by 18 percent, the biggest increase in five years. Shares also closed above their 200-day moving average, a bullish technical signal.
Apple swung between gains and losses a day after reporting results. The stock hit a record high in early trading but shares ended down 1.6 percent at $130.56, weighing on the Nasdaq. Continuación...