The big boys iPad Air 2 and the iPad Pro may have been grabbing the headlines, but it is the smaller sibling iPad mini's lineup that has become the blue-eyed boy among all the Apple tablet offerings.

A survey conducted by the Consumer Intelligence Research Partners (CIRP), which was released on Thursday, reveals that in Q4 2015, the iPad mini lineup emerged as the best-selling Apple tablet series.

The iPad mini lineup, which is composed of the iPad mini, iPad mini 2, iPad mini 3 and iPad mini 4 cumulatively accounted for 47 percent sales in Q4 2015. By comparison, in Q4 2014, the lineup (without the iPad mini 4) accounted for 32 percent sales cumulatively.

So what boosted the sales of the 7.9-inch iPad mini?

"For the first time, iPad mini format had a greater share of sales than the iPad Air Format. iPad mini did much better in the quarter than it did a year ago, in part because of the lower price points along with holiday price promotions, and because of the different models available," said Mike Levin, partner and co-founder of CIRP.

The CIRP based its conclusions on the findings from a survey conducted on 500 Apple customers in the United States. These customers, surveyed from Dec. 26, 2015 to Jan. 12, 2016, had purchased either an iPhone, Mac or iPad in the country from October to December 2015.

The survey also revealed that the best-selling individual iPad from Apple in Q4 2015 was the 9.7-inch iPad Air 2. However, the combined sales from the iPad Air and iPad Air 2 paled in front of the iPad mini lineup, standing at 40 percent.

For those wondering which tablet from the iPad mini lineup was the most popular with consumers in Q4 2015, it's the the iPad mini 2 released in 2013. This was possibly due to its cost effectiveness. The latest-gen iPad mini 4 released in 2015 followed suit, beating the iPad mini 3, which accounted for a marginal sales share.

What may have dissuaded consumers from purchasing an iPad mini 3 could have been the fact that it is basically an iPad mini 2 with Touch ID in tow. The other difference is that it comes in a gold color option.

How did the 12.9-inch iPad Pro fare you wonder? The biggest Apple tablet seems to have found favor with consumers and the two-in-one device notched up 12 percent sales in the period. This augurs well for the iPad Pro as it is off to a positive start despite its high price point of $799.