Silicon Valley, Calif. -- In their largest-ever joint investment, with Palo Alto-based Accel Partners and Menlo Park-based Sequoia Capital said on Tuesday they will invest $70 million in Utah-based Qualtrics, a developer of data collection and analysis software. The company plans to use the funds to expand its web-based product offerings beyond market research and accelerate its growth, beginning with the hiring of another 250 employees in the next year. Qualtrics, which has never before accepted outside funding, said it been profitable since its inception. Clients include Barnes & Noble, CVS Caremark, GEICO, Microsoft, Neiman Marcus, Royal Caribbean, Southwest Airlines, Thomson Reuters, Toyota, Vodafone and Zappos. "Qualtrics is the biggest software company you haven't heard of yet," said Bryan Schreier, a partner at Sequoia Capital. "They've become the foundation of market research and customer analytics for thousands of very happy customers."