The data was gathered following a survey of only 500 mobile users who activated "a new or used phone in the October-December 2014 period" in the US. Thus, there's certainly a margin of error that we should take into consideration. Even so, it's safe to assume that Apple has had a fantastic quarter when it comes to iPhone sales. This is also evidenced by a report from earlier this month, which had it that iOS' market share rose to 47.4% in November in the US, while Android's market share lost a couple of percents, reaching 48.4%.
Needless to say, the iPhone 6 and iPhone 6 Plus (both released at the end of Q3) are mainly responsible for Apple's (probably record-breaking) quarter. They are Apples's largest and thinnest iPhones ever - allowing the company to finally have handsets that are similar in size to what the competition is offering. CIRP notes that, according to its survey, 25% of Samsung users and 18% of LG users who activated a handset last quarter switched to an iPhone. Is anyone surprised?
source: CIRP (PDF) via MacRumors