A federal judge in San Francisco has certified a class of Twitter Inc. investors in a lawsuit accusing the company and two executives of misleading investors about the growth of its daily user base in the run-up to a 40 percent drop in its stock price in 2015.

U.S. District Judge Jon Tigar, in an order dated Monday and posted to the docket Tuesday, granted a motion to certify a class of investors who purchased Twitter stock between Feb. 6 and July 28, 2015. Investor plaintiffs allege that during that period, Twitter’s then-CEO and chief financial officer touted the company’s monthly active user numbers to investors when its flagging daily active user base was what the company put more weight on internally.