According to new data from The NPD Group, one-in-four iPad purchases are made by first-time Apple owners. The Apple Ecosystem Study found that 33 percent of US homes own Apple products, and while a majority—69 percent—of those own iPods, iPad ownership is growing. While 70 percent of long-standing Apple owners report that an iPod was their first Apple product, that number declines to just 57 percent among those buying their first Apple…