Summary Box: Groupon sizzles in public debut

STOCK SOARS: After pricing Thursday at $20, above its expected range, Groupon’s stock rose $6.11 Friday, or 31 percent, to end its first day of trading at $26.11.

HIGH VALUE: This gave the online group deals pioneer a market value of nearly $17 billion ? second only to Google Inc. among tech companies at the time of their initial public offerings.

DOUBTS LINGER: Analysts concerns about Groupon’s business model remain, and the first-day pop was largely expected because the company offered only 5.5 percent of its available stock.