* Sept pvt sector jobs data better than expected
* Yellen scheduled to speak later in the day
* Ralph Lauren jumps after CEO says stepping down
* Western Digital rises after Unisplendour investment
* Indexes up: Dow 1.09 pct, S&P 1.24 pct, Nasdaq 1.49 pct (Updates to open)
By Tanya Agrawal
Sept 30 (Reuters) - Wall Street was sharply higher on Wednesday, helped by gains in energy and health care stocks, but the three major indexes were set for their worst quarter since 2011.
The third quarter was rocked by highly volatile trading due to fears of slowing growth in China. Adding to investors' uncertainty, the U.S. Federal Reserve held off on raising rates at its September meeting.
Investors will be keen to put the bruising quarter behind them and look ahead to the third-quarter earnings season, which begins next week.
Data on Wednesday showed that the U.S. private sector added more jobs than expected in September, raising hopes of a strong reading in the government's payrolls report due Friday.
The Fed has said it needs to see more improvement in the labor market and be confident that inflation will increase before raising rates. Inflation remains below the Fed's 2 percent target.
"The ADP numbers were consistent with what we've been seeing in the last few months with the labor market continuing to tighten," said Peter Cardillo, chief market economist at Rockwell Global Capital in New York.
"It's only a matter of time before the Fed raises rates but I don't think that will happen in October."
Investors will look for clues on the timing of a rate hike when Fed Chair Janet Yellen and St. Louis Fed President James Bullard speak at a conference in St. Louis later on Wednesday.
Yellen said last week the central bank remained on track to raise rates this year. The Fed meets next on Oct. 27-28.
At 9:46 a.m. ET (1346 GMT), the Dow Jones industrial average was up 175.64 points, or 1.09 percent, at 16,224.77, the S&P 500 was up 23.4 points, or 1.24 percent, at 1,907.49 and the Nasdaq composite was up 67.42 points, or 1.49 percent, at 4,584.74.
Apple's 1 percent gain provided the biggest boost to the S&P and the Nasdaq.
All 10 major S&P sectors were higher, with the energy index's 2.18 percent rise leading the advancers. Exxon was up 1.6 percent, while Chevron rose 2.3 percent.
The Nasdaq biotechnology index was up 3.8 percent as investors continued to seek bargains in the sector, which took a beating after Democratic presidential candidate Hillary Clinton criticized drug pricing last week.
Although the market's recent rout has forced many strategists to slash year-end expectations, a Reuters poll shows the S&P 500 is expected to end 2015 roughly 11 percent above current levels.
Shares of Ralph Lauren were up 11.9 percent at $116.46 after the fashion powerhouse said its founder and CEO was stepping down and being replaced by the head of Gap's Old Navy division. Gap was down 6.9 percent at $28.12.
Western Digital jumped 11.9 percent to $77.70 after the data storage company said it would receive a $3.78 billion investment from Chinese infotech company Unisplendour. Rival Seagate rose 7.5 percent to $44.90.
Advancing issues outnumbered decliners on the NYSE by 2,323 to 456. On the Nasdaq, 1,933 issues rose and 434 fell.
The S&P 500 index showed one new 52-week high and two new lows, while the Nasdaq recorded 15 new highs and 31 new lows. (Reporting by Abhiram Nandakumar and Tanya Agrawal; Editing by Saumyadeb Chakrabarty)